Some time ago, I’ve wrote a small server in PHP. Nothing fancy. It would listen on a socket and when a new client would connect, the server would start a new thread and manage the client’s request. Since threading it’s not available in PHP, I’ve emulated the threads with child processes which are available in php. A thread object simply encapsulates a new process started with pnctl_fork() and emulates – to some extent – the behaviour of the java.lang.Thread class, the main difference being that in my implementation, you don’t extend the Thread class, you simply provide the name of a callback function in the constructor.
A simple multithreaded application would look like this:
require_once( 'Thread.php' ); // test to see if threading is available if( ! Thread::available() ) { die( 'Threads not supported' ); } // function to be ran on separate threads function paralel( $_limit, $_name ) { for ( $index = 0; $index < $_limit; $index++ ) { echo 'Now running thread ' . $_name . PHP_EOL; sleep( 1 ); } } // create 2 thread objects $t1 = new Thread( 'paralel' ); $t2 = new Thread( 'paralel' ); // start them $t1->start( 10, 't1' ); $t2->start( 10, 't2' ); // keep the program running until the threads finish while( $t1->isAlive() && $t2->isAlive() ) { }
This will display Now running thread 1 and Now running thread 2 messages with 1 second delays. I know, not that impressive, but hey, it’s multithreaded.
PHP threading will only work on Unix and Linux systems, because pnctl_fork is nothing more than a wrapper for the fork() function from unistd.h and it’s not available under Microsoft operating systems.
I know that the first example was pretty lame, but there are some more interesting things you could do with threads in PHP. For instance, if you need to do some server side processing of all the images in a directory, a multithreaded approach will be much faster.
require_once( 'Thread.php' ); // test to see if threading is available if( ! Thread::available() ) { die( 'Threads not supported' ); } // define the function to be run as a separate thread function processImage( $_image ) { // expensive image processing logic here } $threads = array(); $index = 0; foreach( new DirectoryIterator( '/path/to/images' ) as $item ) { if( $item->isFile() ) { $threads[$index] = new Thread( 'processImage' ); $threads[$index]->start( $item->getPathname() ); ++$index; } } // wait for all the threads to finish while( !empty( $threads ) ) { foreach( $threads as $index => $thread ) { if( ! $thread->isAlive() ) { unset( $threads[$index] ); } } // let the CPU do its work sleep( 1 ); }
PS: it’s a bad practice to keep looping in order to wait for a thread to finish. An ongoing empty loop will quickly boost your CPU ’s load to 100%. If you need your processor free (and you need it), simply send the current (looping) thread to sleep and let the others execute.
// wait for thread - bad approach (overloads the CPU) while ( $thread->isAlive() ) { } // wait for thread - correct approach while( $thread->isAlive() ) { sleep( 1 ); }
Download Thread.php
Here you go: Thread.php. Just click the link to download the class. If you have a better approach to this issue or think that the original class could be improved, don’t be shy and leave a comment below. Credits will be given.
Thanks!
Did you try it on a live project? Can we see it at work?
Unfortunatelly “live” , “at work” no because of M$ OS.
But i’ll use it for my scripts in Ubuntu!
I’ve used it on a project, but it’s only available in intranet. But it works and that’s all that matters. If you have any suggestions of improvement, so share
Hi guys,
My PC worked not correctly, too much mistakes and buggs. Please, help me to fix buggs on my computer.
My operation system is Win Vista.
Thx,
upsemshop
At line 170, there is an error.
pcntl_waitpid( $this->pid, $status = 0 );
You never use the variable $status anyway, so it doesn’t hurt. But if you ever decide to use the $status variable, passing in $status = 0 does not pass the variable to the function, it passes the value of the assignment, 0.
If you set your error reporting to strict, it will complain that:
“Only variables should be passed by reference”
Otherwise, thanks for sharing your code.
10x man, I’ll look into it and fix it later today. Sometime bugs escape one programmer just to be caught by another. That’s the beauty of Open Source.
I had a look at the code and it seems it was better the way it was. I made some tests, and, as if turned out, if I change that line and remove the $status variable, like such:
it will yield an fatal error, saying:
//Fatal error: Only variables can be passed by reference in Thread.php on line 170I always want to pass in 0 as an argument there, so there are two ways in which that can be achieved:
Hope it’s clear for everybody now.
Why do you want to pass a zero in there? That parameter is not expecting a _value_, it’s expecting a _reference_. PHP can can put the real status value in it and give it back to you so that you can check against it later.
See the functions pcntl_wif*()
I hope that made sense.
I’ve browsed the manual, as this entry is over one year old and I can’t remember why I took some decisions back then. It seems that you must always pass in a variable for the status to the function, in order to work. I’m not interested in the returned status, so I’ve passed in a zero variable.