Get PHP memory limit in bytes

memory_limit.php

<?php

function getMemoryLimitBytes()
{
    $limit = ini_get('memory_limit');
    if ($limit == -1) return 0;

    $units = [1 => 'K', 'M', 'G'];
    $unit = strtoupper(substr($limit, -1));
    if ($exp = array_search($unit, $units)) {
        return (int)substr($limit, 0, -1) * pow(1024, $exp);
    }
    else return (int)$limit;
}