How to debug "Fatal error: Allowed memory size of xxx bytes exhausted" in PHP

Question

What is the best strategy to debug a "Fatal error: Allowed memory size of 268435456 bytes exhausted " error? This error i'm getting is strange and something is obviously wrong. The function which is causing it is

/**
 * Flush all output buffers for PHP 5.2.
 *
 * Make sure all output buffers are flushed before our singletons our destroyed.
 *
 * @since 2.2.0
 */
function wp_ob_end_flush_all() {
    $levels = ob_get_level();
    for ($i=0; $i<$levels; $i++)
        ob_end_flush();
}

i simply rebased some code i was working on and started getting this. what's your strategy to debug this?

Answer 1

Try the below code, if your code reaches the specified number of bytes it just echo it and exit. instead of crashing :

function wp_ob_end_flush_all() {
    $levels = ob_get_level();
    for ($i=0; $i<$levels; $i++){
        ob_end_flush();
        if(memory_get_peak_usage() > 268435400) { // 268435456 
            echo memory_get_peak_usage(). ' reached! now we should stop the script.' ;
            break; // or die();
        } 
    }
}

Update To answer your question, one way to debug leaking is to use xdebug another way it to use the function I gave in the example or wrap your suspicious functions by memory_get_usage and compare the difference.

Answer 2

I was also getting this error upon starting the Apache server with EasyPhp-Devserver-16.1.

In my case, it was because Easy php was trying to load a too large error.log file.

Deleting the old server log in

C:\Program Files (x86)\EasyPHP-Devserver-16.1\eds-binaries\httpserver\apache2418x160331124251\logs

and creating an empty one solved my problem.

Hope this can help others.