CODEWITHSUNDEEP
phpregexvalidation
Mohammad Naji
Mohammad Naji

Reputation: 5442

stating number of characters in regex

I want that the usernames be 4-32 chars long.

function validate_username($input)
{
    return (bool) preg_match('/^([a-z]+[a-z0-9_]*){4,32}$/i', $input);
}

What is wrong with my try, please?

var_dump(validate_username('h_q8Y')); which returns FALSE

But var_dump(validate_username('h_q8Yewre_')); returns TRUE

Upvotes: 2

Views: 77

Answers (3)

Shiplu Mokaddim
Shiplu Mokaddim

Reputation: 57690

Your regular expression is wrong. Here

  • ([a-z]+[a-z0-9_]*) matches h_q8Y.
  • Then {4,32} means there will be at least 4 or at most 32 of h_q8Y. But you provided only one h_q8Y.

Hence its not working.

Its better you use following expression.

/^[a-z]\w{3,31}$/i

Upvotes: 2

mario
mario

Reputation: 145512

{4,32} repeats the inner paranthesis match 4 times. You need at least 4 letters to satisfy it.

To assert the length you need a lookahead assertion which is independent from the character class specifier:

 preg_match('/^(?=.{4,32})([a-z]+[a-z0-9_]*)$/i'

                   |             |
             asserts length      |
                            checks char mix

Upvotes: 5

Martin Ender
Martin Ender

Reputation: 44289

You are repeating your repetition 4 to 32 times. I assume that you wanted to make sure that the username starts with a letter. In this case, this is probably what you are looking for:

preg_match('/^[a-z]\w{3,31}$/i', $input);

Note that \w is equivalent to [a-zA-Z0-9_].

Upvotes: 3

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