Convert number with unit byte to bytes unit & get maximum file upload size of php

gistfile1.php

<?php

/**
 * Convert number with unit byte to bytes unit
 * @link https://en.wikipedia.org/wiki/Metric_prefix
 * @param string $value a number of bytes with optinal SI decimal prefix (e.g. 7k, 5mb, 3GB or 1 Tb)
 * @return integer|float A number representation of the size in BYTES (can be 0). otherwise FALSE
 */
function str2bytes($value) {
	// only string
	$unit_byte = preg_replace('/[^a-zA-Z]/', '', $value);
	$unit_byte = strtolower($unit_byte);
	// only number (allow decimal point)
	$num_val = preg_replace('/\D\.\D/', '', $value);
	switch ($unit_byte) {
		case 'p':	// petabyte
		case 'pb':
			$num_val *= 1024;
		case 't':	// terabyte
		case 'tb':
			$num_val *= 1024;
		case 'g':	// gigabyte
		case 'gb':
			$num_val *= 1024;
		case 'm':	// megabyte
		case 'mb':
			$num_val *= 1024;
		case 'k':	// kilobyte
		case 'kb':
			$num_val *= 1024;
		case 'b':	// byte
			return $num_val *= 1;
			break; // make sure
		default:
			return FALSE;
    }
    return FALSE;
}

/**
 * The maximum file upload size by getting PHP settings
 * @return integer|float file size limit in BYTES based
 */
function maximum_upload_size() {
	static $upload_size = NULL;
	if ($upload_size === NULL) {
		$post_max_size = str2bytes( ini_get('post_max_size') );
		$upload_max_filesize = str2bytes( ini_get('upload_max_filesize') );
		$memory_limit = str2bytes( ini_get('memory_limit') );
		// Even though we disable all of variables in php.ini. These still use default value
		// Nearly impossible but check for sure
		if (empty($post_max_size) && empty($upload_max_filesize) && empty($memory_limit)) {
			return FALSE;
		}
		$upload_size = min($post_max_size, $upload_max_filesize, $memory_limit);
	}
	return $upload_size;
}