I can't get preg_match to test if the entire string matches the regex

Question

I\'m using this regular expression to test if a username is valid:

[A-Za-z0-9 _]{3,12} when I test it for matches in a text editor with the string

Answer 1

You should add start and end anchors (^$):

if(!preg_match('/^[A-Za-z0-9 _]{3,12}$/', $content)

The anchor ^ matches the start of the string and $ matches the end. That way, it will only match if the whole string satisfies your regex.

Hope that helps