php preg_match multiple patterns conditionally

Question

I have 2 serial number formats and if either of them match I want to redirect the page to the specified URL. Here's my code which has 2 regexes ORed followed by an ORed conditional statement that uses a group from the regexes:

$snregex = "/^(FL3)20([0-9]{2})([0-9]{2})([0-9]{5})$|^S[XNS][42][10][0]-([0-9]{2})([0-9]{2})([0-9]{2})-[0-9]{4}$/";
if (preg_match($snregex, $sn, $matches)) {
    $mm = $matches[1];
    $yr = $matches[2];
    $wk = $matches[3];

    # If SN MM codes are 25 or FL3 then use host server         
    if ($matches[1] == 'FL3' || $matches[1] == '25') {
        $url = "http://192.168.10.115/logs/20" . $yr . "/" . $wk . "/" . $sn . "/";

        # Redirect to host server
        redirect($url, '303');

The code only works for whatever regex I put in first in the preg_match conditional statement i.e. if the FL3 regex is first then I can successfully match the serial number but not the other. Likewise if I change that statement to have the '25' serial number first I can successfully match that serial number but not the other. Is there something wrong with the following:

$snregex = "/^(FL3)20([0-9]{2})([0-9]{2})([0-9]{5})$|^S[XNS][42][10][0]-([0-9]{2})([0-9]{2})([0-9]{2})-[0-9]{4}$/";

Example valid serial numbers are:

FL320150500022

SS210-251509-0098

Try grouping the ors something like /^(?:(FL3)20([0-9]{2})([0-9]{2})([0-9]{5})|^S[XNS][42][10][0]-([0-9]{2})([0-9]{2})([0-9]{2})-[0-9]{4})$/ Without samples can't test further. — chris85
– chris85, Commented Jun 30, 2015 at 16:00
You may write two different preg_match tests (opposed to your complex combined one), one for each regexp, then your pb become a simple php OR test. It also should be a lot easier to read and maintain... — Armage
– Armage, Commented Jun 30, 2015 at 16:03
Since your patterns are totally unclear, could you show for the two example strings where are the year, the month, and the week? — Casimir et Hippolyte
– Casimir et Hippolyte, Commented Jun 30, 2015 at 16:59

Sjon · Accepted Answer · 2015-06-30 16:08:48Z

1

You should var_dump($matches); then you'll see that ^(a)$|^(b)$ results in 2 groups, not 1 that contains either 'a' or 'b'. This means you should update your if-statement to something like if ($matches[1] == 'FL3' || $matches[5] == '25').

Obviously I don't know the rest of your code; but I would not mix multiple regexps like this; instead I'd spit it into two separate if-statement:

if (preg_match(FL...))
    $url = '...';
elseif (preg_match(25))
    $url = '...';

answered Jun 30, 2015 at 16:08

Sjon

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