PHP: Change memory_limit in shutdown handler after OOM

oom_example.php

<?php
ini_set('memory_limit', '2M');

function shutdownHandler()
{
        print "Shutdown handler triggered\n";
        print "Memory limit: ". ini_get('memory_limit') ."\n";
        // If the next line is commented, a second OOM will be triggered
        ini_set('memory_limit', '-1');
        print "Memory limit: ". ini_get('memory_limit') ."\n";
        print "Mem usage: ". memory_get_usage(true) ."\n";

        $a = '';
        $a .= str_repeat("Hello", 1024 * 1024);
        print "Mem usage: ". memory_get_usage(true) ."\n";
}
register_shutdown_function('shutdownHandler');

print "Memory Limit is: ". ini_get('memory_limit');

$a = '';
while (true) {
    $a .= str_repeat("Hello", 1024 * 1024);
}