Increases PHP memory limit. Keeps the current setting if the current limit is large enough.

increase_memory_limit.php

<?php

function _parse_memory_limit(string $value): int
{
    if (preg_match('/^([0-9]+)([KMG]?)$/', strtoupper($value), $matches) !== 1) {
        throw new RuntimeException('Invalid value for memory_limit: ' . $value);
    }

    [, $number, $multiplier] = $matches;

    $number = (int) $number;

    if ($multiplier !== '') {
        $pos = strpos('KMG', $multiplier);
        $number *= 1024 ** ($pos + 1);
    }

    return $number;
}

function increase_memory_limit(string $value): void
{
    $current = ini_get('memory_limit');

    if ($current === '-1') {
        // already unlimited
        return;
    }

    if ($value === '-1') {
        // set to unlimited
        ini_set('memory_limit', '-1');
        return;
    }

    $currentInt = _parse_memory_limit($current);
    $valueInt   = _parse_memory_limit($value);

    if ($valueInt > $currentInt) {
        ini_set('memory_limit', $value);
    }
}