Regex to validate the input rules

Question

I want to validate using regex the user input to see if match the following rules.

Valid input:

2-000000000000
1-234342324342
...

Rules:

It has to be 13 digit numbers, no string.
Allow hyphen - come after the first character.
Allow space before and after the hyphen - character.

Here's what I tried in PHP, but still not correct:

if(preg_match("/[0-9?\-[0-9]/i])) {

  echo "matched";

}

Maybe preg_match("/^\d ?- ?\d{12}\z/", $string)? Note your string literal is malformed. Also, [0-9?\-[0-9] is a malformed regex that matches a digit, ?, - or [ chars. i is irrelevant here, there are no letters in the pattern. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 2, 2022 at 6:49
It has to be 13 digit numbers, no string. - regex works only on strings, also 2-000000000000 is not even a number in first place — Justinas
– Justinas, Commented Sep 2, 2022 at 6:56
@WiktorStribiżew - it works, thank for that. Regarding the space, how to allow one or more space? I test it and its only match one space, but I want to allow one or more spaces before and after the hyphen. — mana
– mana, Commented Sep 2, 2022 at 6:59
@mana: I have already provisioned for any no of spaces in my comment above — anubhava
– anubhava, Commented Sep 2, 2022 at 6:59

Wiktor Stribiżew · Accepted Answer · 2022-09-02 07:00:24Z

1

Note your double-quoted string literal is malformed, the closing " is missing.

Also, mind that [0-9?\-[0-9] is a malformed regex that matches a digit, ?, - or [ char. The i flag is irrelevant here, since there are no letters in the pattern.

I suggest using

preg_match("/^\d *- *\d{12}\z/", $string)

If the spaces can be any whitespace, replace the literal spaces with \s.

Note the use of \z anchor, I prefer it to $ in validation scenarios, since $ can match before the final line feed char in the string.

See the regex demo (\z replaced with $ since the input is a single multiline string there).

answered Sep 2, 2022 at 7:00

Wiktor Stribiżew

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