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23236 views · 3 years ago
Is PHP a dying language

It seems like this question gets asked every year, as for some reason the perception surrounding PHP is that it is a language used by hobbyists, or a dying language - a programming language on its way out.

Before we take a look at "is PHP being used less," let's start with some critical points to consider when choosing a programming language to learn/ invest in.

PHP powers ~80% of the web


The first point is how popular PHP is as a program language. Recently in a podcast a debate around PHP was raised, with the question being is it an "enterprise" language. The argument against PHP is that it is not widely adopted by enterprises for enterprise application development - or apps that are traditionally developed in Java or .Net.

The key here is understanding that every tool has its strengths and weaknesses, and there are times where using a compiled language such as Java is a smarter move than using PHP. As always, you want to choose the right tool for the job, and PHP as a programming language excels for web applications. That's why today it powers nearly 80% of the websites on the internet! I want to repeat that number, nearly 80% of websites on the internet!

In the podcast, after the initial argument that PHP was not an enterprise language, I had one question to ask - "can you name one enterprise that doesn't use PHP?" Despite the misconception that PHP is not an enterprise language, nearly every enterprise utilizes PHP in some fashion (many for their website, blog, or internal tools). While PHP may not power the app they offer as a service (although for many companies it does), it powers just as critical of offerings that help drive success for the company.

PHP made Yahoo, Facebook, and Tumblr possible


It's not just personal blogs running on a WordPress install, or small sites running on Drupal (btw, both of these power high traffic, well known web properties), but PHP actually makes development for the web easier and faster. Because it is not a compiled language and is designed to scale, companies are able launch faster, add new features as they go, and grow to enormous scale.

Some of the sites that started with PHP include Yahoo, Facebook, Tumblr, Digg, Mailchimp, and Wikipedia! But it's not just older platforms that started off and have grown to scale with PHP - Etsy, Slack, Baidu, Box, and Canva also got started with PHP! Read why Slack chose PHP

In fact, according to BuiltWith, PHP powers 53.22% of the top 10k websites!

Programming languages don't just disappear


Understanding the prevalence of PHP today, and how often it is used is critical to understanding the longevity of PHP. Despite the radicalized idea, programming languages (and thus programming jobs) do not just disappear overnight. Today you can still find jobs writing code used in mainframes - such as Fortran or Cobol.

As long as companies have applications that use PHP, they'll need someone who knows PHP to maintain the application. And with PHP actively being developed and maintained (PHP 8 having just been released), and PHP powerhouses like WordPress, Drupal, SugarCRM, and others powering websites and apps around the world, it's a safe bet PHP won't be going anywhere anytime soon.

But with the basics out of the way, let's look at how PHP has faired over the years.

PHP usage over the years


While there is no exact measurement that determines how programming languages are ranked, there are several different rankings we can look at to see how a language has evolved over the years, and where it ranks today.

GitHub's most popular programming languages


Every year GitHub releases a report of the most popular languages being used to create repositories on GitHub.com. While this isn't an exact way to quantify a programming language, it does help us understand what languages developers are using and promoting for their applications. It also helps us see how lively the community itself is.

In 2014, PHP was ranked as the 3rd most popular programming language, being beat out only by JavaScript and Java. With the emergence of Typescript, C# moving open source, and increased usage of Python for AI - PHP did drop - and was the 6th most popular programming language on GitHub for 2020.

PHP on GitHub over the years

PHP's ranking on the Tiobe index


Another index for software popularity is the Tiobe index, which bases their ratings off of the number of search engines for programming languages. This index is heavily relied on by companies when making programming and investment decisions, especially in developer marketing.

Like with GitHub, PHP has also seen a decline in the Tiobe index. Ranked 8th last year for all languages, PHP dropped to 9th place, being outranked by the C languages (C, C#, C++), Java, Visual Basic, Python, JavaScript, and Assembly. However, to put the rankings in contrast, PHP is 9th out of the 274 languages Tiobe tracks, and bests SQL, Ruby, Groovy, Go, and Swift.

You can see the latest Tiobe index (updated monthly) at: https://www.tiobe.com/tiobe-index/

PHP's ranking on BuiltWith


The last model we'll look at is BuiltWith. BuiltWith scans website headers to determine what a website is powered by, and like GitHub and Tiobe provides a ranking of programming language popularity and trends.

Builtwith provides an interesting perspective in that we can see an explosion of sites being built with PHP (nearly tripling from 2013 to 2016) before dropping and normalizing in 2017. From 2017 to present, the number of sites using PHP has remained almost constant.

BuiltWith PHP Usage

This suggests (as with what we've seen with GitHub and Tiobe) that other languages have grown in popularity, such as JavaScript and Node.js. This doesn't mean that PHP is no longer being used or relied or, but rather that there is more competition and that there are other viable options whereas PHP stood alone at times in terms of being the goto language for web development.

Indeed, when we look at how PHP ranks amongst all technologies on BuiltWith, PHP receives the following BuiltWith awards:

• The most popular on the Entire Internet in Frameworks category.

• The most popular in the Top 10k sites in Frameworks category.

• The most popular in the Top 100k sites in Frameworks category.

• The most popular in the Top 1 Million sites in Frameworks category.

Conclusion


PHP's popularity has dropped from its height 10 years ago, however it still remains the most popular programming language powering the web. It's important to remember that every tool has pros and cons, and some of the bad rap PHP gets is when compared to languages designed to accomplish tasks or build programs that PHP was never designed to.

It's also important to remember a lot of early criticism for PHP came from it being a procedural programming language and not encompassing Object Oriented Programming capabilities. These capabilities were added in PHP 4 and with PHP 7 & 8 OOP has become a staple of the PHP language.

PHP is a viable, powerful language used by nearly every enterprise and many businesses large and small. In fact it powers over 50% of the top 10,000 websites on the web! With such large usage, popular tools such as WordPress, and an active community, it is safe to assume that PHP will remain a prominent language for years to come.
22210 views · 5 years ago
Making Charts and Graphs using Laravel

Installing composer

Composer is a package management tool for PHP. Laravel requires composer for installation. We can download composer from https://getcomposer.org/download/

After installation that you can test whether composer installed or not by command
composer

Installing Laravel

The current stable version of laravel is laravel 5.6. We can install laravel package with three ways.

In command prompt or terminal by running composer global require "laravel/installer" and then Laravel new

or

We can create the project with Composer by running composer create-project --prefer-dist laravel/laravel

or

Directly clone from github
git clone https://github.com/laravel/laravel/tree/master and after that composer update

Laravel local development server

Run the below command in command prompt or terminal
PHP artisan serve


Above command will start to local development servehttp://localhost:8000 or if you want to change default port:

php artisan serve --port 


Generating charts and graphs

We are using consoletvs package for generating charts. So for installation we can first move inside to our project using command prompt or terminal. We are following the below steps to install

Step 1:

First we need to install ConsoleTVs/Charts composer package inside our laravel project.
composer require consoletvs/charts


Step 2:

After successfully installation of above package, open app/config.php and add service provider.
In config/app.php


'providers' => [
....
ConsoleTVs\Charts\ChartsServiceProvider::class,
],


After the service provider we need to add alias
'aliases' => [
....
'Charts' => ConsoleTVs\Charts\Facades\Charts::class,
]



Step 3

We need to configure of database for application. We can configure in either .env file or config/database.php file.


Step 4

We can migrate our default tables that is user. We can find the table in database/migration folder.

Step 5

We can generate dummy records for demo in users table. For creating dummy records, we need to run the below command in command prompt or terminal
php artisan tinker>>> factory(App\User::class, 20)->create();

the above command will create a set of 20 records.

If we need to add more records we need to run the above command or we can increase the count as much as we want. For example
php artisan tinker>>> factory(App\User::class, 2000)->create();


Step 6Creating controller

For creating controller we need to run below command in terminal or command prompt
php artisan make controller:<controller_name>


Step 7Adding the routes

We can add the routes for navigating our application. You can find routes file inside routes folder. Before 5.4 we can find routes.php file itself, now its web.php. If you are using laravel 5.2 routes.php will inside app/http folder.

So inside web.php:

Route::get('create-chart/{type}','ChartController@makeChart');


Here type will be the parameter we are passing and it will focus to makeChart() function inside chartcontroller

Step 8

Import charts to controller, for that in the namespace section add:

Use charts;


Step 9

We can put the below code into chartController

public function makeChart($type)
{
switch ($type) {
case 'bar':
$users = User::where(DB::raw("(DATE_FORMAT(created_at,'%Y'))"),date('Y'))
->get();
$chart = Charts::database($users, 'bar', 'highcharts')
->title("Monthly new Register Users")
->elementLabel("Total Users")
->dimensions(1000, 500)
->responsive(true)
->groupByMonth(date('Y'), true);
break;
case 'pie':
$chart = Charts::create('pie', 'highcharts')
->title('HDTuto.com Laravel Pie Chart')
->labels(['Codeigniter', 'Laravel', 'PHP'])
->values([5,10,20])
->dimensions(1000,500)
->responsive(true);
break;
case 'donut':
$chart = Charts::create('donut', 'highcharts')
->title('HDTuto.com Laravel Donut Chart')
->labels(['First', 'Second', 'Third'])
->values([5,10,20])
->dimensions(1000,500)
->responsive(true);
break;
case 'line':
$chart = Charts::create('line', 'highcharts')
->title('HDTuto.com Laravel Line Chart')
->elementLabel('HDTuto.com Laravel Line Chart Lable')
->labels(['First', 'Second', 'Third'])
->values([5,10,20])
->dimensions(1000,500)
->responsive(true);
break;
case 'area':
$chart = Charts::create('area', 'highcharts')
->title('HDTuto.com Laravel Area Chart')
->elementLabel('HDTuto.com Laravel Line Chart label')
->labels(['First', 'Second', 'Third'])
->values([5,10,20])
->dimensions(1000,500)
->responsive(true);
break;
case 'geo':
$chart = Charts::create('geo', 'highcharts')
->title('HDTuto.com Laravel GEO Chart')
->elementLabel('HDTuto.com Laravel GEO Chart label')
->labels(['ES', 'FR', 'RU'])
->colors(['#3D3D3D', '#985689'])
->values([5,10,20])
->dimensions(1000,500)
->responsive(true);
break;
default:
break;
}
return view('chart', compact('chart'));
}


Step 10

Create a blade file. Blade is the view file used inside the laravel. You can add new blade file with any name with an extension of .blade.php
Here we are creating chart.blade.php

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>My Charts</title>
{!! Charts::styles() !!}
</head>
<body>

<div class="app">
<center>
{!! $chart->html() !!}
</center>
</div>

{!! Charts::scripts() !!}
{!! $chart->script() !!}
</body>
</html>


Step 11

We can run our laravel application in local development server by php artisan serve command:

http://localhost:8000/create-chart/bar
http://localhost:8000/create-chart/pie
http://localhost:8000/create-chart/donut
http://localhost:8000/create-chart/line
http://localhost:8000/create-chart/area
http://localhost:8000/create-chart/geo



In the above example we was creating line chart, geo chart, bar chart, pie chart, donut chart, line chart and area chart. We can also create gauge chart, progressbar chart, areaspline chart, scatter chart, percentage chart etc using consoletvs charts composer package.

There are a lot of jQuery libraries also available like amcharts, chartjs, highcharts, google, material, chartist, fusioncharts, morris, plottablejs etc. However, using this plugin we can easily create charts without having to use jQuery, another advantage to building it in with Laravel.
19467 views · 5 years ago
Generate PDF from HTML in Laravel 5.7

Today, I will share with you how to create a PDF file from HTML blade file in Laravel 5.7. We will be using dompdf package for generating the PDF file.

In the below example, we will install barryvdh/laravel-dompdf using composer package and thereafter we will add new route url with controller. Then we will create a blade file. Then after we have to just run project with serve and we can check the PDF file is for download.

Download Laravel 5.7

Now I am going to explain the step by step from scratch with laravel installation for dompdf. To get started, we need to download fresh Laravel 5.7 application using command, so open our terminal and run the below command in the command prompt:

composer create-project --prefer-dist laravel/laravel blog


Install laravel-dompdf Package

Now we will install barryvdh/laravel-dompdf composer package by using the following composer command in ourLlaravel 5.7 application.

composer require barryvdh/laravel-dompdf


Then the package is successfully installed in our application, after that open config/app.php file and we need to add alias and service provider.
config/app.php

'providers' => [
....
Barryvdh\DomPDF\ServiceProvider::class,
],

'aliases' => [
....
'PDF' => Barryvdh\DomPDF\Facade::class,
]


Create Routes

Now we need to create routes for the items listing. so now open our "routes/web.php" file and we need to add following route.
routes/web.php

Route::get('demo-generate-pdf','HomeController@demoGeneratePDF');


Create Controller

Here,we need to create a new controllerHomeController (mostly it will be there, we can skip this step if we don't need to create a controller) that will manage our pdf generation using the generatePDF() method of route.
app/Http/Controllers/HomeController.php

<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use PDF;

class HomeController extends Controller
{
public function demoGeneratePDF()
{
$data = ['title' => 'Welcome to My Blog'];
$pdf = PDF::loadView('myPDF', $data);

return $pdf->download('demo.pdf');
}
}


Create Blade File

In the final step, let us create demoPDF.blade.php in the resources/views/demoPDF.blade.php for structure of pdf file and add the following code:
resources/views/demoPDF.blade.php

<!DOCTYPE html>
<html>
<head>
<title>Hi</title>
</head>
<body>
<h1>Welcome to My BLOG - {{ $title }}</h1>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
</body>
</html>


Now run the below command for serve and test it:

php artisan serve

16359 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.
13108 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.

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