Question

I have a PHP class that creates a PNG image on the fly and sends it to browser. PHP manual says that I need to make sure that imagedestroy function is called at end to release the memory. Now, if I weren’t using a class, I would have some code like this:

function shutdown_func()  {     global $img;     if ($img)         imagedestroy($img); } register_shutdown_function('shutdown_func'); 

However, I believe that appropriate place for my class would be to place a call to imagedestroy in class’ destructor.

I failed to find out if destructors get called the same way shutdown functions does? For example, if execution stops when user presses the STOP button in browser.

Note: whatever you write in your answer, please point to some article or manual page (URL) that supports it.

Answer 1

I just tested with Apache, PHP being used as Apache module. I created an endless loop like this:

<?php class X {     function __destruct()     {         $fp = fopen('/var/www/htdocs/dtor.txt', 'w+');         fputs($fp, 'Destroyed\n');         fclose($fp);     } };  $obj = new X(); while (true) {     // do nothing } ?> 

Here’s what I found out:

• pressing STOP button in Firefox does not stop this script
• If I shut down Apache, destructor does not get called
• It stops when it reaches PHP max_execution_time and destuctor does not get called

However, doing this:

<?php function shutdown_func() {     $fp = fopen('/var/www/htdocs/dtor.txt', 'w+');     fputs($fp, 'Destroyed2\n');     fclose($fp); } register_shutdown_function('shutdown_func');  while (true) {     // do nothing } ?> 

shutdown_func gets called. So this means that class destuctor is not that good as shutdown functions.