[Solved] Regex for Username and Password verification

Question

You need to anchor your pattern and use lookahead to validate those cases.

if(preg_match('/^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])[a-zA-Z0-9@:.]+$/', $username)) { ... }

(?= ... ) is a zero-width assertion which does not consume any characters on the string.

Therefore, It only matches a position in the string. The point of zero-width is the validation to see if a regular expression can or cannot be matched looking ahead from the current position, without adding to the overall match.

Accepted Answer

You need to anchor your pattern and use lookahead to validate those cases.

if(preg_match('/^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])[a-zA-Z0-9@:.]+$/', $username)) { ... }

(?= ... ) is a zero-width assertion which does not consume any characters on the string.

Therefore, It only matches a position in the string. The point of zero-width is the validation to see if a regular expression can or cannot be matched looking ahead from the current position, without adding to the overall match.