PHP & Web Development Blogs

For those of you not familiar with the concept of underclocking: it's the opposite of overclocking, that is, you don't speed up CPU but instead slow it down..

What for?

Ask the underclockers, I'm totally not sure. Actually, hanging around the Web these days leaves a feeling that nearly every website out there must have been underclocked, but most of the time it's about tons of unnecessary images, megabytes of javascript (of which hardly a hundred kilobytes gets actually executed), and all that. In this post I will, however, tell you about a server-side approach to underclocking, with a help of our good old friend - the MySQL Database Server.

Today I had a nice chat in my client's development telegram channel. The two other devs, R** and V**, were making a switch of the old image API app to a new MySQL server. A couple of days before that, we have discussed a plan, it was as dumb as possible, just as I like it. Super-simple clear steps that a five-year-old can make. Switch to readonly mode (stop uploads), dump DB, restore the dump on the new server, update database connection details, turn off readonly mode. What could possibly go wrong?

Nothing. Except that it did go wrong. The app that I'm talking about, is a really ancient piece of what is gently called "legacy". Once the app was back to normal again, we noticed a significant slowdown on every page that made use of images. Before that point, I never got to that app and/or its database. I logged in to the MySQL console, and started investigating, at the same point chatting with colleagues.

Me: Is that really important that the tables are MyISAM? It's 2018, you know.. There are dozens of queries in queue waiting for table-level locks.

R**: Are they MyISAM? Really?

Me: Yes.. Any objection against converting them to InnoDB? With the current state of the website, with all those tons of Gateway Timeouts, it's not going to make it worse if I do it right now..

    . minutes later:

Me: Nah, it didn't help a lot.. But, looking at the SHOW PROCESSLIST output, I see something weird. What, do you think, this query does? SELECT LAST_INSERT_ID() FROM images? 

R**: ehh... Gets you the last AUTO_INCREMENT id from images table?

Me: Let's play another good news bad news joke.. Good news: you're right, it gets you the last AUTO_INCREMENT id. Bad news: it's not for table, it's for the session. Worse news: this query gets you the last AUTO_INCREMENT id and does it exactly as many times as there are rows in the images table. how many are there?

R**: about 8mln. #@%&! It's sending 8mln rows on every image upload, through the network!

Me: Bingo! 8mln rows, with one and the same integer value in all of them.

R**: Ouch... Aaaand... Before today, it was not an issue. Because the database was on the same server as the application..

Me: Exactly, it used the loopback interface, and now it's using ehternet, which, apparently, doesn't have a super good bandwidth. We don't have a gigabit channel between servers, do we?

R**: No, it's 100 Mbit

Me: Are you fixing the query, BTW?

R**: yeah, man, deploying it...

Another 10 minutes later, problem is gone, performance is back to normal.

What conclusions can one make from this story?

I can think of two at least:
First: never underestimate legacy code. The ways it can move to bite you in the ass, are mysterious.
Second: if you're working with MySQL or another RDBMS, learn SQL, learn the specific SQL dialect you're using and learn how to trouble shoot issues. In this case, I did not need to look in the PHP code at all in order to help my fellow colleagues out. You can also generalize this principle as "you have to know the tools you're using".

Happy optimizing, folks! Comments appreciated!

Hey there! This reading is not going to be a technical one. Instead, it's just a little portion of information that you might have not known before. I once worked for a project that did currency exchanges. As you probably know, currencies have 3-letter codes (ISO 4217), and I asked myself if there's a currency with code "PHP".

PHP: Philippine peso! In Philippines you can code PHP for PHP!


But there's more to it.. "PHP: Prvi Hrvatski Pištolj" stands for "first Croatian pistol". Next time someone tells me that it's too easy to shoot your own leg with PHP, I'll definitely agree.
If you don't believe me - checkout these 10 most common mistakes PHP programmers make from Toptal!

Or checkout Eric Wastl's list of things in PHP that make him sad. Or these three weird facts about PHP that you might not have known. The thing is PHP is a great programming language for building web applications, but... it's not without it's quirks.

___What else does PHP stand for???___

Project Honey Pot - system targeted at spammers and email harversters.

Pigeonhole principle - if n items are put into m containers, with n > m, then at least one container must contain more than one item. Mathematicians can be even more weird then programmers, can't they? And remember, programmers can right something like if (true == false)...

PHP has even more meanings, see this wikipedia page) for reference and havePHun!

It's a very common task to work with an array of values, each of the same type. Integers, strings, all kinds of objects etc. But PHP is still a weakly typed language, so it's hard to tell if an arbitrary array actually contains only values of a given type.
Of course, you can always use a class:

class IntArray {
 private $values = [];
public function add(int $value)	{
 $this->values[] = $value;
}
}

Then, whenever you need an array of integers, you may write something like this:

class BatchProcessor
{
 private $ids;
public function __construct(IntArray $ids) {
 $this->ids = $ids;
}
}

Not bad. You'll need a class per type, though, and that may seem a bit of an overkill for such a simple task. Luckily, same result can be achieved differently, but with the same level of confidence in every value type:

class BatchProcessor
{
	private $ids;
public function __construct(int ...$ids) {
 $this->ids = $ids;	}
}

Voila - no need for extra class! This approach uses the PHP 7's type hinting for scalar types, in conjunction with Variable length argument lists available since PHP 5.6. In fact, variable-length argument lists have been around since probably the very first version of the language, but in 5.6 they were revisited and got some nice syntactic sugar in form of "...", so you declare and call them as easy as this:

function func(...$args){...}
$args = [1, 2, 3];
func(...$args);

The approach can work with any type-hinting available in PHP, and I hope you find it somewhat useful! Comment, discuss share and ask questions - I'll be around.

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!

In case you are living under a rock, the latest version of PHP released last week. PHP developers around the world began rebuilding their development containers with it so they can run their tests. Now it’s your turn. If you haven’t already installed it, you can download it here http://php.net/downloads.php Grab it, get it running in your development environment, and run those unit tests. If all goes well, you can begin planning your staged deployment to production.

If you need a quick start guide to get you going, our good friend Mr Colin O’Dell has just the thing for you “Installing PHP 7.1”. It’ll get you up and going quickly on PHP 7.1.

What’s the big deal about PHP 7.1? I am so glad you asked. Here are the major new features released in PHP 7.1.

* Nullable types
* Void return type
* Iterable pseudo-type
* Class constant visiblity modifiers
* Square bracket syntax for list() and the ability to specify keys in list()
* Catching multiple exceptions types

Now if you want a quick intro to several of these new features, check out our “RFCs of the Future” playlist on YouTube. In it, I talk about 4 of the new features.

Oh and while you are watching things download & compile, why not take the time to give a shoutout to all the core contributors, and a special thank you to Davey Shafik and Joe Watkins, the PHP 7.1 release managers.

Cheers!
=C=