PHP regular expression string starting with certain characters and followed by digits

Question

I am trying to create a regular expression to validate a code. The rules are as follows:

It starts with a B or J or 28
Total length of the string must be either 7 or 13 characters (including starting characters)
The characters following the starting characters must be all digits

Can anyone help me with this ? Thanks

I tried something like

$pattern = "/^((J|B|28)([0-9])({7}|{13})?/i";

But it doesn't seem to work :\

MikeM · Accepted Answer · 2013-02-19 10:16:23Z

7

$pattern = "/^(?=(.{7}|.{13})$)(B|J|28)\d+$/";

edited Feb 19, 2013 at 10:16

answered Feb 19, 2013 at 10:10

MikeM

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8 Comments

Mihai Matei Over a year ago

I always had problems with these regular expressions.. I don't know when I will start to learn using them :) good job Mike, I've also tested it and it works +1

Mihai Matei Over a year ago

Change it to /^(?=(.{7}|.{13})$)(B|J|28)\d+$/ and will work

Daniel Booker-Macedo Over a year ago

Vote up for speed; but would rather see the edit explaining the subpatterns, delimiter use, back reference, etc... That's what contributes to getting DjMike (and everyone else) to the next level :) On a side note, his is case insensitive, yours isn't.

Comforse Over a year ago

@Daniel true, my understanding of regular expressions is horrible :\

kjetilh Over a year ago

Have to admit clever use of the conditional check here, you can further simplify by changing ?=(.{7}|.{13} to ?=(.{7,13}

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kjetilh · Accepted Answer · 2013-02-19 10:37:15Z

1

First use the following regular expression to match the pattern. It will capture the first identifier in the first group and the following digits in the second group.

<?php 
$pattern = "/^(B|J|28)([0-9]+)$/i"; 
?>

Then run strlen() to validate the length. Regular expressions are not a good tool to validate variable lengths across groups.

<?php 
$hasValidLength = strlen( $str ) === 7 || strlen( $str ) === 13; 
?>

edited Feb 19, 2013 at 10:37

answered Feb 19, 2013 at 10:06

kjetilh

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6 Comments

Abdelilah Over a year ago

He said total length must be between 7-13 including starting characters

Comforse Over a year ago

i'll check. Thanks for the answers!

kjetilh Over a year ago

Wops. Then he should rather do a strlen() check after running the regular expression.

Comforse Over a year ago

It doesn't match this for example: J100027872577

Oscar Mederos Over a year ago

I think the idea (of the question) is to have a single regular expression to match against the code.

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