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15393 views · 5 years ago

Implement Web Push Notification in PHP using W3C provided Notification API

Hi Guys,
I am sharing you the simple steps by which you can broadcast the web push notifications to your subscriber. In this tutorial we are making a subscriber form and saving information using Ajax and PHP and then through a server side code returning response to current logged in user and showing notification to that user.
Following are the steps to build this system

1. Create a database, I am creating db with name 'web_notifications'

Creating subscribers and notifications tables using following sql statements


CREATE TABLE IF NOT EXISTS <code>subscribers</code> (
 <code>id</code> int(11) NOT NULL,
 <code>name</code> varchar(255) NOT NULL,
 <code>email</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>subscribers</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>subscribers</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;



CREATE TABLE IF NOT EXISTS <code>notifications</code> (
 <code>id</code> int(11) NOT NULL,
 <code>to_user</code> int(11) NOT NULL,
 <code>title</code> varchar(255) NOT NULL,
 <code>body</code> varchar(255) NOT NULL,
 <code>url</code> varchar(255) NOT NULL,
 <code>is_sent</code> int(11) NOT NULL DEFAULT '0',
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>notifications</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>notifications</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

2. Now create a db_connect.php file with following code

<?php 
session_start();
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "web_notifications";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
 die("Connection failed: " . $conn->connect_error);
} 
?>

3. Create a cookies.js file to read and write browser cookies

function WriteCookie(key,content) {
 var now = new Date();
 now.setMonth( now.getMonth() + 1 ); 
 document.cookie = key+"=" + escape(content) + ";";
 document.cookie = "expires=" + now.toUTCString() + ";"
}

function ReadCookie(key) {
 var allcookies = document.cookie;
 cookiearray = allcookies.split(';');
 var CookieData=Array();
 for(var i=0; i<cookiearray.length; i++) {
 k = cookiearray[i].split('=')[0];
 v = cookiearray[i].split('=')[1];
 CookieData[k]=v;
 }
 return CookieData[key];
}

4. Create a ajax file to read and mark is_sent if any notification foun to be sent in database for that user. create file with name 'fetch_notifications.php' with following content

<?php require 'db_connect.php';

$sql = "SELECT id,title,body,url FROM notifications where to_user='".@$_GET['user_id']."' and is_sent='0' ";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 $data[]=$row;

 $upd = "update notifications set is_sent='1' where id='".$row['id']."' ";
 $conn->query($upd);

 }
}

if(count($data)>0)
{
 $response=array("status"=>1,"notification"=>$data);
}
else
{
 $response=array("status"=>0,"error"=>"No new notification!");
}

echo json_encode($response);

$conn->close(); 
?>

5. Now code index.php to show subscriber form and on submit insert record into the subscriber table


<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>Web Push Notification Demo</title>
 <script src="./cookies.js" type="text/javascript"></script>
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['subscribe_form']))
{
 $_SESSION['is_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $useremail=$conn->real_escape_string($_POST['useremail']);


 $sql = "INSERT INTO subscribers set name='".$username."',email='".$useremail."' ";
 if ($conn->query($sql) === TRUE) {
 $_SESSION['is_login']=1;
 $_SESSION['Uid']= $conn->insert_id;
 $_SESSION['Uname']= $username;
 ?>
 <script type="text/javascript">
 WriteCookie("Uid","<?php echo $_SESSION['Uid']; ?>");
 </script> 
 <?php
 $msg="<p style='color:green'>You have subscribe for push notification succesfully :)</p>";
 } else {
 $msg="<p style='color:red'>Error in subscribing for notifications</p>";
 }


}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['is_login']) && $_SESSION['is_login']==1)
{
 ?>
 <h2>Welcome <?php echo $_SESSION['Uname']; ?></h2>
 <script type="text/javascript"> 

setInterval(function(){ 
 check_notification(); 
}, 10000);

function check_notification()
{ 
 var Uid=ReadCookie("Uid");
 if(Uid!==undefined)
 {
 $.ajax({url: "fetch_notifications.php?user_id="+Uid, success: function(result){ 
 var response=JSON.parse(result);
 if(response.status==1)
 {
 
 response=response.notifications;
 for (var i = response.length - 1; i >= 0; i--) {
 var url = response[i]['url'];
 var noti = new Notification(response[i]['title'], {
 icon: 'logo.png', body: response[i]['body'],
 });
 noti.onclick = function () {
 window.open(url); 
 noti.close(); 
 };
 
 };

 }
 else{
 console.log(response.error);

 }
 
 }

 }); 
 }
}

 
 </script>
 <?php
}
else
{
 ?>
 <h2 class="text-center">Subscribe for Notifications</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> Information</h3>
 <p class="m-0">provide your information</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input Your Name Here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-envelope text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="useremail" name="useremail" pattern="[^@\s]+@[^@\s]+\.[^@\s]+" title="Invalid email address" placeholder="[email protected]" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Subscribe" name="subscribe_form" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The frontend of your subscription page (index.php) should look like this:

Subscribing Form to User

Now we are ready to receive notification in frontend, but we still need to create an admin page from where we can send notification to subscriber(s).

6. Create a table for admin user




CREATE TABLE IF NOT EXISTS <code>admin</code> (
 <code>id</code> int(11) NOT NULL,
 <code>username</code> varchar(255) NOT NULL,
 <code>password</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>admin</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>admin</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

INSERT INTO <code>web_notifications</code>.<code>admin</code> (<code>id</code>, <code>username</code>, <code>password</code>, <code>createdAt</code>) VALUES (NULL, 'admin', MD5('123456'), CURRENT_TIMESTAMP);

Following is the code for admin.php to add the notifications to subscriber(s) account also i have inserted following login credentials for admin in admin table:
username:admin
password:123456

7. Now put following code in admin.php

<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>ADMIN PAGE</title> 
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['login']))
{
 $_SESSION['admin_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $password=$conn->real_escape_string($_POST['password']);
 $sql = "SELECT * FROM admin where username='".$username."' and password='".md5($password)."' ";
 $result = $conn->query($sql);
 if ($result->num_rows > 0) {
 $_SESSION['admin_login']=1;
 $msg="<p style='color:green'>Admin Logged-in Successfully :)</p>";
 }
 else {
 $msg="<p style='color:red'>INVALID CREDENTIALS FOR ADMIN</p>";
 } 


}
if(isset($_POST['add_notification']))
{ 
 $title=$conn->real_escape_string($_POST['title']);
 $body=$conn->real_escape_string($_POST['body']);
 $url=$conn->real_escape_string($_POST['url']);
 $users=$_POST['users'];

 foreach ($users as $user_id) {
 $ins = "insert into notifications set to_user='".$user_id."' , title='".$title."', url='".$url."', body='".$body."' ";
 $conn->query($ins);
 }
 $msg="<p style='color:green'>Notification(s) added to subscribers account.</p>";
 
}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['admin_login']) && $_SESSION['admin_login']==1)
{
 ?>
 <h2>Welcome Admin, Send notification to Subscriber(s)</h2>

<form method="post">
 
 

<div class="form-group">
 <label for="sel1">Select Subscriber(s):</label>
 <select multiple="multiple" required="required" class="form-control" id="users" name="users[]">
 <?php
$sql = "SELECT id,name FROM subscribers";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 echo "<option value='".$row['id']."'>".$row['name']."</option>";
 }
}
?>
 </select>
</div>

 <div class="form-group">
 <label for="email">Title</label>
 <input type="text" required class="form-control" placeholder="notification title here" name="title" id="title">
 </div>
 
 <div class="form-group">
 <label for="email">Message</label>
 <textarea required class="form-control" placeholder="notification message here" name="body" id="body"></textarea> 
 </div>

 <div class="form-group">
 <label for="email">Url</label>
 <input type="url" required class="form-control" placeholder="notification landing/click url here" name="url" id="url">
 </div>
 
 <input type="submit" class="btn btn-primary btn-block" name="add_notification" value="Submit" />

</form>


 <?php
}
else
{
 ?>
 <h2 class="text-center">ADMINISTRATOR</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> LOGIN</h3>
 <p class="m-0">provide admin login credentials</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input username here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-key text-info"></i></div>
 </div>
 <input type="password" class="form-control" id="password" name="password" placeholder="your password here" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Login" name="login" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The admin page will ask login credentials first then it will look like following screenshot:

Admin Send Notifiv=cation to subscribers

Now in your project if you open index.php you have a frontend where user will register themselves to receive notifications, and admin.php is your backend where you can send notifications to users or subscribers

If you face any problem in setup this small project please just let me know in the comments below, or by messaging me.

0 · Post Comment Read more

damnjan

7656 views · 5 years ago

Iterator in PHP (A practical guide)

Every time I see this

$users = [new User(), new User()];

I see a lost opportunity to use Iterator.

Why Iterators?

Collections are an awesome way to organize your previously no-named array. There is a couple of reasons why you should use iterators. One of reason stays for behavior, you can specify exact behavior on standard calls such as next, current, valid etc. Other reason could be that you want to ensure that collection contains an only specific type of an object.

Understand a suffer from using an array of unknown value types.
Very common in the PHP world arrays are used to store all kind of data, in many dimensions in many nested forms. Arrays introduced infinite flexibility to the developer, but because of that, they become very evil.

Example:

- Your function (getUsers) returns an array of User objects.
- Another function (setUsersToActiveState) using getUsers output array and set all users active status to true.
- setUsersToActiveState loop through the array and expect to call a specific method on array item. For example, the method name is getActiveStatus.
- If given array is an array of desired objects which have a callable method getActiveStatus, all fine. But if not exception will be thrown.
- How we can ensure that given array is always an array of objects of a specific type?

public function getUsers(): array
{
 
 return $userArray;
}

public function setUsersToActiveState()
{
 $users = $this->getUsers();
 
 foreach ($users as $user) {
 if(!$user->getActiveStatus()) {
 $user->setActiveStatus(true);
 }
 }
}

There immediately two problems occurred.
. One is the problem of type. Our IDE doesn't know what's inside array of $users, so because of that IDE can't suggest us how to use $user element. (I put this comment block above foreach, it works for phpStorm and I guess for some other IDEs)
. Your colleagues! How they possibly know what's inside array if there is no any hint.
. Bonus problem, getUsers can return literally any array and there won't be warning in the system.

Solution


class UsersCollection implements \IteratorAggregate
{
 
 private $users = [];

 public function getIterator() : UserIterator
 {
 return new UserIterator($this);
 }

 public function getUser($position)
 {
 if (isset($this->users[$position])) {
 return $this->users[$position];
 }

 return null;
 }

 public function count() : int
 {
 return count($this->users);
 }

 public function addUser(User $users)
 {
 $this->users[] = $users;
 }
}

class UserIterator implements \Iterator
{
 
 private $position = 0;

 
 private $userCollection;

 public function __construct(UsersCollection $userCollection)
 {
 $this->userCollection = $userCollection;
 }

 public function current() : User
 {
 return $this->userCollection->getUser($this->position);
 }

 public function next()
 {
 $this->position++;
 }

 public function key() : int
 {
 return $this->position;
 }

 public function valid() : bool
 {
 return !is_null($this->userCollection->getUser($this->position));
 }

 public function rewind()
 {
 $this->position = 0;
 }
}

Tests

Off course there is the tests to ensure that our Collection and Iterator works like a charm. For this example I using syntax for PHPUnit framework.

class UsersCollectionTest extends TestCase
{
 
 public function testUsersCollectionShouldReturnNullForNotExistingUserPosition()
 {
 $usersCollection = new UsersCollection();

 $this->assertEquals(null, $usersCollection->getUser(1));
 }

 
 public function testEmptyUsersCollection()
 {
 $usersCollection = new UsersCollection();

 $this->assertEquals(new UserIterator($usersCollection), $usersCollection->getIterator());

 $this->assertEquals(0, $usersCollection->count());
 }

 
 public function testUsersCollectionWithUserElements()
 {
 $usersCollection = new UsersCollection();
 $usersCollection->addUser($this->getUserMock());
 $usersCollection->addUser($this->getUserMock());

 $this->assertEquals(new UserIterator($usersCollection), $usersCollection->getIterator());
 $this->assertEquals($this->getUserMock(), $usersCollection->getUser(1));
 $this->assertEquals(2, $usersCollection->count());
 }

 private function getUserMock()
 {
 }
}


class UserIteratorTest extends MockClass
{
 
 public function testCurrent()
 {
 $iterator = $this->getIterator();
 $current = $iterator->current();

 $this->assertEquals($this->getUserMock(), $current);
 }

 
 public function testNext()
 {
 $iterator = $this->getIterator();
 $iterator->next();

 $this->assertEquals(1, $iterator->key());
 }

 
 public function testKey()
 {
 $iterator = $this->getIterator();

 $iterator->next();
 $iterator->next();

 $this->assertEquals(2, $iterator->key());
 }

 
 public function testValidIfItemInvalid()
 {
 $iterator = $this->getIterator();

 $iterator->next();
 $iterator->next();
 $iterator->next();

 $this->assertEquals(false, $iterator->valid());
 }

 
 public function testValidIfItemIsValid()
 {
 $iterator = $this->getIterator();

 $iterator->next();

 $this->assertEquals(true, $iterator->valid());
 }

 
 public function testRewind()
 {
 $iterator = $this->getIterator();

 $iterator->rewind();

 $this->assertEquals(0, $iterator->key());
 }

 private function getIterator() : UserIterator
 {
 return new UserIterator($this->getCollection());
 }

 private function getCollection() : UsersCollection
 {
 $userItems[] = $this->getUserMock();
 $userItems[] = $this->getUserMock();

 $usersCollection = new UsersCollection();

 foreach ($userItems as $user) {
 $usersCollection->addUser($user);
 }

 return $usersCollection;
 }

 private function getUserMock()
 {
 }
}

Usage

public function getUsers(): UsersCollection
{
 $userCollection = new UsersCollection();
 
 foreach ($whatIGetFromDatabase as $user) {
 $userCollection->addUser($user);
 }
 return $userCollection;
}

public fucntion setUsersToActiveState()
{
 $users = $this->getUsers();

 foreach ($users as $user) {
 if(!$user->getActiveStatus()) {
 $user->setActiveStatus(true);
 }
 }
}

As you can see setUsersToActiveState remains the same, we only do not need to specify for our IDE or collagues what type $users variable is.

Extending functionalities

Believe or not you can reuse this two objects and just change names of variables to fit most of the needs. But if you want any more complex functionality, than feel free to add it in iterator or collection.

Example 1

For example, let's say that userCollection accepts only users with age more than 18. Implementation will happen in UsersCollection class in the method addUser.

 public function addUser(User $users)
 {
 if ($user->getAge() > 18) {
 $this->users[] = $users;
 } 
 }

Example 2

You need to add bulk users. Then you can expand your userCollection with additional method addUsers and it might look like this.


 public function addUsers(array $users)
 {
 foreach($users as $user) {
 $this->addUser(User $users);
 }
 }

0 · Post Comment Read more

dmamontov

16069 views · 5 years ago

PHP IPC with Daemon Service using Message Queues, Shared Memory and Semaphores

Introduction

In a previous article we learned about Creating a PHP Daemon Service. Now we are going to learn how to use methods to perform IPC - Inter-Process Communication - to communicate with daemon processes.

Message Queues

In the world of UNIX, there is an incredible variety of ways to send a message or a command to a daemon script and vice versa. But first I want to talk only about message queues - "System V IPC Messages Queues".

A long time ago I learned that a queue can be either in the System V IPC implementation, or in the POSIX implementation. I want to comment only about the System V implementation, as I know it better.

Lets get started. At the "normal" operating system level, queues are stored in memory. Queue data structures are available to all system programs. Just as in the file system, it is possible to configure queues access rights and message size. Usually a queue message size is small, less than 8 KB.

This introductory part is over. Lets move on to the practice with same example scripts.queue-send.php

$key = ftok(__FILE__, 'A'); 
$queue = msg_get_queue($key);

msg_send($queue, 1, 'message, type 1');
msg_send($queue, 2, 'message, type 2');
msg_send($queue, 3, 'message, type 3');
msg_send($queue, 1, 'message, type 1');

echo "send 4 messages
";

queue-receive.php

$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

for ($i = 1; $i <= 3; $i++) {
 echo "type: {$i}
";

 while ( msg_receive($queue, $i, $msgtype, 4096, $message, false, MSG_IPC_NOWAIT) ) {
 echo "type: {$i}, msgtype: {$msgtype}, message: {$message}
";
 }
}

Lets run on the first stage of the file queue-send.php, and then queue-receive.php.

u% php queue-send.php
send 4 messages
u% php queue-receive.php
type: 1
type: 1, msgtype: 1, message: s:15:"message, type 1";
type: 1, msgtype: 1, message: s:15:"message, type 1";
type: 2
type: 2, msgtype: 2, message: s:15:"message, type 2";
type: 3
type: 3, msgtype: 3, message: s:15:"message, type 3";

You may notice that the messages have been grouped. The first group gathered 2 messages of the first type, and then the remaining messages.

If we would have indicated to receive messages of type 0, you would get all messages, regardless of the type.

while (msg_receive($queue, $i, $msgtype, 4096, $message, false, MSG_IPC_NOWAIT)) {

Here it is worth noting another feature of the queues: if we do not use the constant MSG_IPC_NOWAIT in the script and run the script queue-receive.php from a terminal, and then run periodically the file queue-send.php, we see how a daemon can effectively use this to wait jobs.queue-receive-wait.php

$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

while ( msg_receive($queue, 0, $msgtype, 4096, $message) ) {
 echo "msgtype: {$msgtype}, message: {$message}
";
}

Actually that is the most interesting information of all I have said. There are also functions to get statistics, disposal and checking for the existence of queues.

Lets now try to write a daemon listening to a queue:queue-daemon.php

$pid = pcntl_fork();
$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

if ($pid == -1) {
 exit;
} elseif ($pid) {
 exit;
} else {
 while ( msg_receive($queue, 0, $msgtype, 4096, $message) ) {
 echo "msgtype: {$msgtype}, message: {$message}
";
 }
}

posix_setsid();

Shared Memory

We have learned to work with queues, with which you can send small system messages. But then we may certainly be faced with the task of transmitting large amounts of data. My favorite type of system, System V, has solved the problem of rapid transmission and preservation of large data in memory using a mechanism calledShared Memory.

In short, the data in the Shared Memory lives until the system is rebooted. Since the data is in memory, it works much faster than if it was stored in a database somewhere in a file, or, God forgive me on a network share.

Lets try to write a simple example of data storage.shared-memory-write-base.php

$id = ftok(__FILE__, 'A');


$shmId = shm_attach($id);

$var = 1;

if (shm_has_var($shmId, $var)) {
 $data = (array) shm_get_var($shmId, $var);
} else {
 $data = array();
}

$data[time()] = file_get_contents(__FILE__);

shm_put_var($shmId, $var, $data);

Run this script several times to save the value in memory. Now lets write a script only to read from the memory.shared-memory-read-base.php

$id = ftok(__DIR__ . '/shared-memory-write-base.php', 'A');
$shmId = shm_attach($id);
$var = 1; 

if (shm_has_var($shmId, $var)) {
 $data = (array) shm_get_var($shmId, $var);
} else {
 $data = array();
}

foreach ($data as $key => $value) {
 $path = "/tmp/$key.php";
 file_put_contents($path, $value);

 echo $path . PHP_EOL;
}

Semaphores

So, in general terms, it should be clear for you by now how to work with shared memory. The only problems left to figure out are about a couple of nuances, such as: "What to do if two processes want to record one block of memory?" Or "How to store binary files of any size?".

To prevent simultaneous accesses we will use semaphores. Semaphores allow us to flag that we want to have exclusive access to some resource, like for instance a shared memory block. While that happens other processes will wait for their turn on semaphore.

In this code it explained clearly:shared-memory-semaphors.php


$id = ftok(__FILE__, 'A');

$semId = sem_get($id);

sem_acquire($semId);

$data = file_get_contents(__DIR__.'/06050396.JPG', FILE_BINARY);

$shmId = shm_attach($id, strlen($data)+4096);
$var = 1;
 
if (shm_has_var($shmId, $var)) {
 $data = shm_get_var($shmId, $var);

 $filename = '/tmp/' . time();
 file_put_contents($filename, $data, FILE_BINARY);

 shm_remove($shmId);
} else {
 shm_put_var($shmId, $var, $data); 
}

sem_release($semId);

Now you can use the md5sum command line utility to compare two files, the original and the saved file. Or, you can open the file in image editor or whatever prefer to compare the images.

With this we are done with shared memory and semaphores. As your homework I want to ask you to write code that a demon will use semaphores to access shared memory.

Conclusion

Exchanging data between the daemons is very simple. This article described two options for data exchange: message queues and shared memory.

Post a comment here if you have questions or comments about how to exchange data with daemon services in PHP.

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dmamontov

12596 views · 5 years ago

Creating a PHP Daemon Service

What is a Daemon?

The term daemon was coined by the programmers of Project MAC at MIT. It is inspired on Maxwell's demon in charge of sorting molecules in the background. The UNIX systems adopted this terminology for daemon programs.

It also refers to a character from Greek mythology that performs the tasks for which the gods do not want to take. As stated in the "Reference System Administrator UNIX", in ancient Greece, the concept of "personal daemon" was, in part, comparable to the modern concept of "guardian angel." BSD family of operating systems use the image as a demon's logo.

Daemons are usually started at machine boot time. In the technical sense, a demon is considered a process that does not have a controlling terminal, and accordingly there is no user interface. Most often, the ancestor process of the deamon is init - process root on UNIX, although many daemons run from special rcd scripts started from a terminal console.

Richard Stevenson describes the following steps for writing daemons:
. Resetting the file mode creation mask to 0 function umask(), to mask some bits of access rights from the starting process.
. Cause fork() and finish the parent process. This is done so that if the process was launched as a group, the shell believes that the group finished at the same time, the child inherits the process group ID of the parent and gets its own process ID. This ensures that it will not become process group leader.
. Create a new session by calling setsid(). The process becomes a leader of the new session, the leader of a new group of processes and loses the control of the terminal.
. Make the root directory of the current working directory as the current directory will be mounted.
. Close all file descriptors.
. Make redirect descriptors 0,1 and 2 (STDIN, STDOUT and STDERR) to /dev/null or files /var/log/project_name.out because some standard library functions use these descriptors.
. Record the pid (process ID number) in the pid-file: /var/run/projectname.pid.
. Correctly process the signals and SigTerm SigHup: end with the destruction of all child processes and pid - files and / or re-configuration.

How to Create Daemons in PHP

To create demons in PHP you need to use the extensions pcntl and posix. To implement the fast communication withing daemon scripts it is recommended to use the extension libevent for asynchronous I/O.

Lets take a closer look at the code to start a daemon:

umask(0);
$pid = pcntl_fork(); 
if ($pid < 0) {
 print('fork failed');
 exit 1; 
}

After a fork, the execution of the program works as if there are two branches of the code, one for the parent process and the second for the child process. What distinguishes these two processes is the result value returned the fork() function call. The parent process ID receives the newly created process number and the child process receives a 0.

if ($pid > 0) { echo "daemon process started
";
 exit;
} 
 
$sid = posix_setsid();
if ($sid < 0) {
 exit 2;
}

chdir('/');
file_put_contents($pidFilename, getmypid() ); 
run_process();

The implementation of step 5 "to close all file descriptors" can be done in two ways. Well, closing all file descriptors is difficult to implement in PHP. You just need to open any file descriptors before fork(). Second, you can override the standard output to an error log file using init_set() or use buffering using ob_start() to a variable and store it in log file:

ob_start();
var_dump($some_object);
$content = ob_get_clean();
fwrite($fd_log, $content);

Typically, ob_start() is the start of the daemon life cycle and ob_get_clean() and fwrite() calls are the end. However, you can directly override STDIN, STDOUT and STDERR:

ini_set('error_log', $logDir.'/error.log');
fclose(STDIN); 
fclose(STDOUT);
fclose(STDERR);
$STDIN = fopen('/dev/null', 'r'); 
$STDOUT = fopen($logDir.'/application.log', 'ab');
$STDERR = fopen($logDir.'/application.error.log', 'ab');

Now, our process is disconnected from the terminal and the standard output is redirected to a log file.

Handling Signals

Signal processing is carried out with the handlers that you can use either via the library pcntl (pcntl_signal_dispatch()), or by using libevent. In the first case, you must define a signal handler:

function sig_handler($signo)
{
 global $fd_log;
 switch ($signo) {
 case SIGTERM:
 fclose($fd_log); unlink($pidfile); exit;
 break;
 case SIGHUP:
 init_data(); break;
 default:
 }
}


pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGHUP, "sig_handler");

Note that signals are only processed when the process is in an active mode. Signals received when the process is waiting for input or in sleep mode will not be processed. Use the wait function pcntl_signal_dispatch(). We can ignore the signal using flag SIG_IGN: pcntl_signal(SIGHUP, SIG_IGN); Or, if necessary, restore the signal handler using the flag SIG_DFL, which was previously installed by default: pcntl_signal(SIGHUP, SIG_DFL);

Asynchronous I/O with Libevent

In the case you use blocking input / output signal processing is not applied. It is recommended to use the library libevent which provides non-blocking as input / output, processing signals, and timers. Libevent library provides a simple mechanism to start the callback functions for events on file descriptor: Write, Read, Timeout, Signal.

Initially, you have to declare one or more events with an handler (callback function) and attach them to the basic context of the events:

$base = event_base_new();
$event = event_new();
$errno = 0;
$errstr = '';
$socket = stream_socket_server("tcp://$IP:$port", $errno, $errstr);
stream_set_blocking($socket, 0);
event_set($event, $socket, EV_READ | EV_PERSIST, 'onAccept', $base);

Function handlers 'onRead', 'onWrite', 'onError' must implement the processing logic. Data is written into the buffer, which is obtained in the non-blocking mode:

function onRead($buffer, $id)
{
 while($read = event_buffer_read($buffer, 256)) {
 var_dump($read);
 }
}

The main event loop runs with the function event_base_loop($base);. With a few lines of code, you can exit the handler only by calling: event_base_loobreak(); or after the specified time (timeout) event_loop_exit();.

Error handling deals with failure Events:

function onError($buffer, $error, $id)
{
 global $id, $buffers, $ctx_connections;
 event_buffer_disable($buffers[$id], EV_READ | EV_WRITE);
 event_buffer_free($buffers[$id]);
 fclose($ctx_connections[$id]);
 unset($buffers[$id], $ctx_connections[$id]);
}

It should be noted the following subtlety: Working with timers is only possible through the file descriptor. The example of official the documentation does not work. Here is an example of processing that runs at regular intervals.

$event2 = event_new();
$tmpfile = tmpfile();
event_set($event2, $tmpfile, 0, 'onTimer', $interval);
$res = event_base_set($event2, $base);
event_add($event2, 1000000 * $interval);

With this code we can have a working timer finishes only once. If we need a "permanent" Timer, using the function onTimer we need create a new event each time, and reassign it to process through a "period of time":

function onTimer($tmpfile, $flag, $interval)
{
 $global $base, $event2;

 if ($event2) {
 event_delete($event2);
 event_free($event2);
 }

 call_user_function(‘process_data’,$args);

 $event2 = event_new();
 event_set($event2, $tmpfile, 0, 'onTimer', $interval);
 $res = event_base_set($event2, $base);
 event_add($event2, 1000000 * $interval);
}

At the end of the daemon we must release all previously allocated resources:

event_delete($event);
event_free($event);
event_base_free($base);

event_base_set($event, $base);
event_add($event);

Also it should be noted that for the signal processing handler is set the flag EV_SIGNAL: event_set($event, SIGHUP, EV_SIGNAL, 'onSignal', $base);

If needed constant signal processing, it is necessary to set a flag EV_PERSIST. Here follows a handler for the event onAccept, which occurs when a new connection is a accepted on a file descriptor:

function onAccept($socket, $flag, $base) {
 global $id, $buffers, $ctx_connections;
 $id++;
 $connection = stream_socket_accept($socket);
 stream_set_blocking($connection, 0);
 $buffer = event_buffer_new($connection, 'onRead', NULL, 'onError', $id);
 event_buffer_base_set($buffer, $base);
 event_buffer_timeout_set($buffer, 30, 30);
 event_buffer_watermark_set($buffer, EV_READ, 0, 0xffffff); event_buffer_priority_set($buffer, 10); event_buffer_enable($buffer, EV_READ | EV_PERSIST); $ctx_connections[$id] = $connection;
 $buffers[$id] = $buffer;
}

Monitoring a Daemon

It is good practice to develop the application so that it was possible to monitor the daemon process. Key indicators for monitoring are the number of items processed / requests in the time interval, the speed of processing with queries, the average time to process a single request or downtime.

With the help of these metrics can be understood workload of our demon, and if it does not cope with the load it gets, you can run another process in parallel, or for running multiple child processes.

To determine these variables need to check these features at regular intervals, such as once per second. For example downtime is calculated as the difference between the measurement interval and total time daemon.

Typically downtime is determined as a percentage of a measurement interval. For example, if in one second were executed 10 cycles with a total processing time of 50ms, the time will be 950ms or 95%.

Query performance wile be 10rps (request per second). Average processing time of one request: the ratio of the total time spent on processing requests to the number of requests processed, will be 5ms.

These characteristics, as well as additional features such as memory stack size queue, number of transactions, the average time to access the database, and so on.

An external monitor can be obtain data through a TCP connection or unix socket, usually in the format of Nagios or zabbix, depending on the monitoring system. To do this, the demon should use an additional system port.

As mentioned above, if one worker process can not handle the load, usually we run in parallel multiple processes. Starting a parallel process should be done by the parent master process that uses fork() to launch a series of child processes.

Why not run processes using exec() or system()? Because, as a rule, you must have direct control over the master and child processes. In this case, we can handle it via interaction signals. If you use the exec command or system, then launch the initial interpreter, and it has already started processes that are not direct descendants of the parent process.

Also, there is a misconception that you can make a demon process through command nohup. Yes, it is possible to issue a command: nohup php mydaemon.php -master >> /var/log/daemon.log 2 >> /var/log/daemon.error.log &

But, in this case, would be difficult to perform log rotation, as nohup "captures" file descriptors for STDOUT / STDERR and release them only at the end of the command, which may overload of the process or the entire server. Overload demon process may affect the integrity of data processing and possibly cause partial loss of some data.

Starting a Daemon

Starting the daemon must happen either automatically at boot time, or with the help of a "boot script."

All startup scripts are usually in the directory /etc/rc.d. The startup script in the directory service is made /etc/init.d/ . Run command start service myapp or start group /etc/init.d/myapp depending on the type of OS.

Here is a sample script text:

#! /bin/sh
#
$appdir = /usr/share/myapp/app.php
$parms = --master –proc=8 --daemon
export $appdir
export $parms
if [ ! -x appdir ]; then
 exit 1
fi

if [ -x /etc/rc.d/init.d/functions ]; then
 . /etc/rc.d/init.d/functions
fi

RETVAL=0

start () {
 echo "Starting app"
 daemon /usr/bin/php $appdir $parms 
 RETVAL=$?
 [ $RETVAL -eq 0 ] && touch /var/lock/subsys/mydaemon
 echo
 return $RETVAL
}

stop () {
 echo -n "Stopping $prog: "
 killproc /usr/bin/fetchmail
 RETVAL=$?
 [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/mydaemon
 echo
 return $RETVAL
}

case in
 start)
 start
 ;;
 stop)
 stop
 ;;
 restart)
 stop
 start
 ;;
 status)
 status /usr/bin/mydaemon
 ;;
 *)
 echo "Usage:

php
if (is_file('app.phar')) {
unlink('app.phar');
}
$phar = new Phar('app.phar', 0, 'app.phar');
$phar->compressFiles(Phar::GZ);
$phar->setSignatureAlgorithm (Phar::SHA1);
$files = array();
$files['bootstrap.php'] = './bootstrap.php';
$rd = new RecursiveIteratorIterator(new RecursiveDirectoryIterator('.'));
foreach($rd as $file){
if ($file->getFilename() != '..' && $file->getFilename() != '.' && $file->getFilename() != __FILE__) {
if ( $file->getPath() != './log'&& $file->getPath() != './script'&& $file->getPath() != '.')
$files[substr($file->getPath().DIRECTORY_SEPARATOR.$file->getFilename(),2)] =
$file->getPath().DIRECTORY_SEPARATOR.$file->getFilename();
}
}
if (isset($opt['version'])) {
$version = $opt['version'];
$file = "buildFromIterator(new ArrayIterator($files));
$phar->setStub($phar->createDefaultStub('bootstrap.php'));
$phar = null;
}

 {start|stop|restart|status}"
 ;;
 
RETVAL=$?
exit $RETVAL

Distributing Your PHP Daemon

To distribute a daemon it is better to pack it in a single phar archive module. The assembled module should include all the necessary PHP and .ini files.

Below is a sample build script:

#php app.phar
myDaemon version 0.1 Debug
usage:
--daemon – run as daemon
--debug – run in debug mode
--settings – print settings
--nofork – not run child processes
--check – check dependency modules
--master – run as master
--proc=[8] – run child processes

Additionally, it may be advisable to make a PEAR package as a standard unix-console utility that when run with no arguments prints its own usage instruction:
[NMD%%CODE%%]

Conclusion

Creating daemons in PHP it is not hard but to make them run correctly it is important to follow the steps described in this article.

Post a comment here if you have questions or comments on how to create daemon services in PHP.

0 · Post Comment Read more

crocodile2u

4620 views · 5 years ago

PHP: Down to the Basics

It's 2018, and you're a top-notch modern web developer, with a load of knowledge and tools right there at your disposal: Google and StackOverflow, debugger with a GUI, IDE with autocomplete, you name it. Occasionally, though, you still find yourself in a plain old text console on a remote server, or you have to do something without IDE, or there is no network connection... In such cases it might be helpful to feel comfortable in a simple terminal. In this post I'm going to list some switches for the PHP command that you can use to get information and some utilities.

Getting basic information about PHP

$ php -i
phpinfo()
PHP Version => 7.2.10-0ubuntu1

System => Linux awesome 4.18.0-10-generic #11-Ubuntu SMP Thu Oct 11 15:13:55 UTC 2018 x86_64
Build Date => Sep 13 2018 13:38:55
Server API => Command Line Interface
Virtual Directory Support => disabled
...

Full information about your PHP interpreter. Pipe the output to the Unix less command in order to get pagination and search: php -i | less. Type Q to exit the less shell. Some distros might lack less, in that case you may try php -i | more, which doesn't give you search but still has pagination.

Want a short summary of which PHP extensions you have? Just ask:

$ php -m
[PHP Modules]
calendar
Core
ctype
date
dom
ds
exif
...

More specific info about core and extensions' functions and classes

Full information about functions and classes provided by an extension:

$ php --re ds
Extension [ <persistent> extension #46 ds version 1.2.6 ] {

 - Dependencies {
 Dependency [ json (Required) ]
 Dependency [ spl (Required) ]
 }

 - Classes [11] {
 Interface [ <internal:ds> interface Ds\Hashable ] {

 - Constants [0] {
 }

 - Static properties [0] {
 }
...

Information on a specific class:

$ php --rc Ds\Vector
Class [ <internal:ds> <iterateable> final class Ds\Vector implements Ds\Sequence, Traversable, Countable, JsonSerializable, Ds\Collection ] {

 - Constants [1] {
 Constant [ public integer MIN_CAPACITY ] { 8 }
 }

 - Static properties [0] {
 }
...

Same for a function:

$ php --rf fopen
Function [ <internal:standard> function fopen ] {

 - Parameters [4] {
 Parameter #0 [ <required> $filename ]
 Parameter #1 [ <required> $mode ]
 Parameter #2 [ <optional> $use_include_path ]
 Parameter #3 [ <optional> $context ]
 }
}

Utilities

Ever found yourself creating a dummy PHP file of just a few lines - only to be run once and then deleted? The -a switch might be what you're looking for:

$ php -a
Interactive mode enabled

php > var_dump(join(", ", [1, 2, 3]));
php shell code:1:
string(7) "1, 2, 3"
php >

It starts an interactive shell so you can type any PHP code and execute it straight away. Requires PHP to be compiled with readline support (most distros have that anyway).

Want a quick check for any parse/syntax errors in a PHP file? Use linter:

$ php -l test.php 
PHP Parse error: syntax error, unexpected 'array_shift' (T_STRING) in test.php on line 4
Errors parsing test.php

It has a web-server!

Yes! Just in case you missed it, as of PHP 5.4.0, the CLI SAPI provides a built-in web server. Want a quick look at a web page generated by an app? Here you go:

$ cd /my_application/document_root
$ php -S localhost:8000

Then open http://localhost:8000/ in your browser of choice and enjoy!

Hope you also have enjoyed this reading. Your feedback and questions are always appreciated!

0 · Post Comment Read more

PHP & Web Development Blogs

Search - PHP & Web Development Blogs

1. Create a database, I am creating db with name 'web_notifications'

2. Now create a db_connect.php file with following code

3. Create a cookies.js file to read and write browser cookies

4. Create a ajax file to read and mark is_sent if any notification foun to be sent in database for that user. create file with name 'fetch_notifications.php' with following content

5. Now code index.php to show subscriber form and on submit insert record into the subscriber table

6. Create a table for admin user

7. Now put following code in admin.php

Why Iterators?

Example:

Solution

Tests

Usage

Extending functionalities

Example 1

Example 2

Introduction

Message Queues

Shared Memory

Semaphores

Conclusion

What is a Daemon?

How to Create Daemons in PHP

Handling Signals

Asynchronous I/O with Libevent

Monitoring a Daemon

Starting a Daemon

Distributing Your PHP Daemon

Conclusion

Getting basic information about PHP

More specific info about core and extensions' functions and classes

Utilities

It has a web-server!

Popular Topics

Popular Blogs

About

Partner

Promote

Support

Member Login

PHP & Web Development Blogs

Search - PHP & Web Development Blogs

1. Create a database, I am creating db with name 'web_notifications'

2. Now create a db_connect.php file with following code

3. Create a cookies.js file to read and write browser cookies

4. Create a ajax file to read and mark is_sent if any notification foun to be sent in database for that user. create file with name 'fetch_notifications.php' with following content

5. Now code index.php to show subscriber form and on submit insert record into the subscriber table

6. Create a table for admin user

7. Now put following code in admin.php

Why Iterators?

Example:

Solution

Tests

Usage

Extending functionalities

Example 1

Example 2

Introduction

Message Queues

Shared Memory

Semaphores

Conclusion

What is a Daemon?

How to Create Daemons in PHP

Handling Signals

Asynchronous I/O with Libevent

Monitoring a Daemon

Starting a Daemon

Distributing Your PHP Daemon

Conclusion

Getting basic information about PHP

More specific info about core and extensions' functions and classes

Utilities

It has a web-server!

Popular Topics

Popular Blogs

About

Partner

Promote

Support