How can I check if a regular expression is not har

问题:

I am working on a project. This project have a user interface that we wrote in PHP. In the management part, there is a form input where the user needs to enter a regular expression. As I know, I can not check if is a regex or not, because every string is a regex. What I want to do is check whether this input is proper or not? Which way I can do it?

回答1:

It's very hard to do this by analysing the regex (short of actually parsing the regex itself.

I suggest you rather use conservative settings for pcre.backtrack-limit and pcre.recursion_limit.

回答2:

It really depends on what you expect the program to do. If you are writing a regex tester, you simply need to have another field where they can input a string to check it against. Then use String.test(/regex/) or String.match(/regex/) to see if it is good for that string.