PHP Regex for a string with alphanumeric and special characters

Question

I tried and could not find an answer for this issue, so I'm asking this question.

I need to create a regex for password validation and it must have following conditions.

• At least one letter
• At least one number
• At least one special letter ~ ! ^ ( ) { } < > % @ # & * + = _ -
• Must not contain $ ` , . / \\ ; : ' " |
• Must be between 8-40 characters
• No spaces

I have created following regex but it does not work properly.

preg_match('/[A-Za-z\d$!^(){}?\[\]<>~%@#&*+=_-]{8,40}$/', $newpassword)

Can somebody please help me to fix this regex properly?

Thanks.

Answer 1

Here you go, using lookaheads to verify your conditions:

^(?=.*[a-zA-Z])(?=.*\d)(?=.*[~!^(){}<>%@#&*+=_-])[^\s$`,.\/\\;:'"|]{8,40}$

Let's break it down a little, because it's kinda nasty-looking:

• The ^ asserts that it's at the start of the string.
• The first lookahead, (?=.*[a-zA-Z]) , verifies that it contains at least one letter (upper or lower).
• The second, (?=.*\\d) , verifies that it contains at least one digit.
• The third, (?=.*[~!^(){}<>%@#&*+=_-]) , verifies that it contains at least one character from your special characters list.
• Finally, [^\\s$,.\\/\\\\;:'"|]{8,40}$ verifies that the entire string is between 8 and 40 characters long, and contains no spaces or illegal characters by using an inverted character class.

Demo on Regex101