Cron expression syntax check (excluding special operators except for * and /)

cron syntax regex.php

<?php

$cron = "*/5 * * * * *";
$result = preg_match(
	"/(\*|[0-5]?[0-9]|\*\/[0-9]+)\s+"
	."(\*|1?[0-9]|2[0-3]|\*\/[0-9]+)\s+"
	."(\*|[1-2]?[0-9]|3[0-1]|\*\/[0-9]+)\s+"
	."(\*|[0-9]|1[0-2]|\*\/[0-9]+|jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\s+"
	."(\*\/[0-9]+|\*|[0-7]|sun|mon|tue|wed|thu|fri|sat)\s*"
	."(\*\/[0-9]+|\*|[0-9]+)?/i", $cron, $matches);