php - How can I validate regex?

Question

I'd like to test the validity of a regular expression in PHP, preferably before it's used. Is the only way to do this actually trying a preg_match() and seeing if it returns FALSE?

Is there a simpler/proper way to test for a valid regular expression?

Answer 1

// This is valid, both opening ( and closing )
var_dump(preg_match('~Valid(Regular)Expression~', '') === false);
// This is invalid, no opening ( for the closing )
var_dump(preg_match('~InvalidRegular)Expression~', '') === false);

As the user pozs said, also consider putting @ in front of preg_match() (@preg_match()) in a testing environment to prevent warnings or notices.

To validate a RegExp just run it against null (no need to know the data you want to test against upfront). If it returns explicit false (=== false), it's broken. Otherwise it's valid though it need not match anything.

So there's no need to write your own RegExp validator. It's wasted time...