[php] ini_set("memory_limit") in PHP 5.3.3 is not working at all

I had this working before :

echo ini_get("memory_limit")."\n";
echo ini_get("memory_limit")."\n";

That would input this :


on a php script executed by command line. I updated from 5.2 to 5.3, and from now, this directive is not working at all : this gives me :


and then make my script fail with a fatal Error...

I checked the php documentation, and googled it, and I didn't find anywhere that "memory_limit" had been deprecated.

Does anyone have a solution?

This question is related to php memory apache2 debian

The answer is

Here's a list of things that are worth checking:

Is Suhosin installed?


  • The format is important ini_set('memory_limit', '512'); // DIDN'T WORK ini_set('memory_limit', '512MB'); // DIDN'T WORK ini_set('memory_limit', '512M'); // OK - 512MB ini_set('memory_limit', 512000000); // OK - 512MB

When an integer is used, the value is measured in bytes. Shorthand notation, as described in this FAQ, may also be used.


  • Has php_admin_value been used in .htaccess or virtualhost files?

Sets the value of the specified directive. This can not be used in .htaccess files. Any directive type set with php_admin_value can not be overridden by .htaccess or ini_set(). To clear a previously set value use none as the value.


Works for me, has nothing to do with PHP 5.3. Just like many such options it cannot be overriden via ini_set() when safe_mode is enabled. Check your updated php.ini (and better yet: change the memory_limit there too).

If you have the suhosin extension enabled, it can prevent scripts from setting the memory limit beyond what it started with or some defined cap.


Ubuntu 10.04 comes with the Suhosin patch only, which does not give you configuration options. But you can install php5-suhosin to solve this:

apt-get update
apt-get install php5-suhosin

Now you can edit /etc/php5/conf.d/suhosin.ini and set:

suhosin.memory_limit = 1G

Then using ini_set will work in a script:

ini_set('memory_limit', '256M');

Let's do a test with 2 examples:

    $memory = (int)ini_get("memory_limit"); // Display your current value in php.ini (for example: 64M)
    echo "original memory: ".$memory."<br>";
    ini_set('memory_limit','128M'); // Try to override the memory limit for this script
    echo "new memory:".$memory;
    // Will display:
    // original memory: 64
    // new memory: 64

The above example doesn't work for overriding the memory_limit value. But This will work:

    $memory = (int)ini_get("memory_limit"); // get the current value
    ini_set('memory_limit','128'); // override the value
    echo "original memory: ".$memory."<br>"; // echo the original value
    $new_memory = (int)ini_get("memory_limit"); // get the new value
    echo "new memory: ".$new_memory;  // echo the new value
    // Will display:
    // original memory: 64
    // new memory: 128

You have to place the ini_set('memory_limit','128M'); at the top of the file or at least before any echo.

As for me, suhosin wasn't the solution because it doesn't even appear in my phpinfo(), but this worked:

    ini_set('memory_limit','2048M'); // set at the top of the file

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