Ini_Set("Memory_Limit") in PHP 5.3.3 Is Not Working at All

ini_set( memory_limit ) in PHP 5.3.3 is not working at all

Most likely your sushosin updated, which changed the default of suhosin.memory_limit from disabled to 0 (which won't allow any updates to memory_limit).

On Debian, change /etc/php5/conf.d/suhosin.ini

;suhosin.memory_limit = 0

suhosin.memory_limit = 2G

Or whichever value you are comfortable with. You can find the changelog of Sushosin at http://www.hardened-php.net/hphp/changelog.html, which says:

Changed the way the memory_limit protection is implemented

PHP memory_limit locked to 256MB?

3 possibles I can think of / find:

Prior to PHP 5.2.1, in order to use this directive it had to be
enabled at compile time by using --enable-memory-limit in the
configure line.

The issue detailed here: ini_set("memory_limit") in PHP 5.3.3 is not working at all

ini_set is disabled

How to increase memory limit for PHP over 2GB?

Have you tried using the value in MB ?

php_value memory_limit 2048M

Also try editing this value in php.ini not Apache.

Is ini_set( memory_limit , 512M ); too much?

Perhaps you're using php to load the whole files into memory before serving them to the user? I've used a function found at http://www.php.net/manual/en/function.readfile.php (comments section) that serves the file in parts, keeping memory low. Copying from that post (because my version is changed):

<?php 
    function readfile_chunked ($filename,$type='array') { 
      $chunk_array=array(); 
      $chunksize = 1*(1024*1024); // how many bytes per chunk 
      $buffer = ''; 
      $handle = fopen($filename, 'rb'); 
      if ($handle === false) { 
       return false; 
      } 
      while (!feof($handle)) { 
          switch($type) 
          { 
              case'array': 
              // Returns Lines Array like file() 
              $lines[] = fgets($handle, $chunksize); 
              break; 
              case'string': 
              // Returns Lines String like file_get_contents() 
              $lines = fread($handle, $chunksize); 
              break; 
          } 
      } 
       fclose($handle); 
       return $lines; 
    } 
?>