Question

I’m a beginner in regular expression so it didn’t take long for me to get totally lost :]

What I need to do:

I’ve got a string of values ‘a:b,a2:b2,a3:b3,a4:b4’ where I need to search for a specific pair of values (ie: a2:b2) by the second value of the pair given (b2) and get the first value of the pair as an output (a2).

All characters are allowed (except ‘,’ which seperates each pair of values) and any of the second values (b,b2,b3,b4) is unique (cant be present more than once in the string)

Let me show a better example as the previous may not be clear:

This is a string: 2 minutes:2,5 minutes:5,10 minutes:10,15 minutes:15,never:0

Searched pattern is: 5

I thought, the best way was to use function called preg_match with subpattern feature.

So I tried the following:

$str = '2 minutes:2,5 minutes:5,10 minutes:10,15 minutes:15,20 minutes:20,30 minutes:30, never:0';

$re = '/(?P<name>\w+):5$/';
preg_match($re, $str, $matches);

echo $matches['name'];

Wanted output was ‘5 minutes’ but it didn’t work.

I would also like to stick with Perl-Compatible reg. expressions as the code above is included in a PHP script.

Can anyone help me out? I’m getting a little bit desperate now, as Ive spent on this most of the day by now …

Thanks to all of you guys.

Answer 1

$str = '2 minutes:2,51 seconds:51,5 minutes:5,10 minutes:10,15 minutes:51,never:0';
$search = 5;

preg_match("~([^,\:]+?)\:".preg_quote($search)."(?:,|$)~", $str, $m);

echo '<pre>'; print_r($m); echo '</pre>';

Output:

Array
(
    [0] => 5 minutes:5
    [1] => 5 minutes
)