PHP - Why am I being warned that my regular expression is too large?

Question

I would like to use a regular expression to validate user input. I want to allow any combination of letters, numbers, spaces, commas, apostrophes, periods, exclamation marks

Answer 1

While I agree that the regex compiler shouldn't behave that way, you really shouldn't have encountered this problem. Inside the parentheses, your regex matches exactly one character from a specific set--the definition of a character class. The correct way to write your regex is to list all the characters inside one set of square brackets and forego the parentheses:

/^[a-z0-9 ,'.!?]{1,4000}$/i

That works fine, as this demo shows. However, it was the parentheses that were causing the error (even non-capturing parens cause it), and that doesn't seem right to me, even if they were unnecessary.