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phpregexpreg-match

Trying to get regex pattern to match any other than letters and single special character

I'm new to regex and am trying to match a very simple pattern but am struggling to get regex. I basically just want test a bunch of strings to check if they contain anything that isn't either in 'a-z' (both lower or upper case) or '_' character. So if a string contains the '@' character I want it to fail.

so far it looks like:

if (!preg_match("/[a-z_]/", $string)) {
     echo "Bad string";
}

But that's failing to pickup anything it seems. Any help would be greatly appreciated.

Solution

  • Use negation in your regex to search for characters you don't want.

    // If the string has any characters other than A-z or _ then echo bad string
if (preg_match("/[^a-zA-Z_]/", $string)) {
     echo "Bad string";
}

    https://regex101.com/r/wKUNjm/2