how can I replace everything apart from...

[king.oslo]

how can I replace everything apart from a sub-pattern?

 

For example, how do I strip everything everything apart from Q or B that are enclosed by ?'s ?

This example strip everything, but I want to strip everything apart from B or Q

<?php
$string = 'LotsOfLetters?B?LotsOfLetters';
$regex = '~\w+\?(B|Q)\?\w+~';
$replace = '';
?>

 

Thanks,

Marius

[JAY6390]

Why not just use preg_match_all and get them that way?

$string = 'LotsOfL?Q?etters?B?LotsOfLe?Q??B?tters';
$regex = '%\?(B|Q)\?%';
preg_match_all($regex, $string, $out);
$string = implode('', $out[0]);
echo $string;

[king.oslo]

How can I do this with preg_replace the way I tried to start?

 

Thanks,

Marius

[nrg_alpha]

Hmm.. if I understand correctly, one way could be to use preg_replace_callback in conjunction with create_function, which is basically an anonymous lamda style function:

 

$string = 'LotsOfL?Q?etters?B?LotsOfLe?Q??B?tters';
echo $string = preg_replace_callback('#(.*?)(?:\?[bQ]\?)?#', create_function('$a', 'return str_replace($a[1], "", $a[0]);'), $string);
// Output: ?Q??B??Q??B?

 

So to visualize the process, it goes something like this:

 

Pattern = #(.*?)(?:\?[bQ]\?)?# (red denotes a captured group)

LotsOfL?Q? = $a[0] - 1^st iteration of the match/capture

LotsOfL = $a[1]

$a[1] gets replaced by empty quotes within $a[0], which leaves ?Q? to be returned.

 

Repeat and rinse..

 

etters?B? = $a[0] - 2^nd iteration of the match/capture

etters = $a[1]

$a[1] gets replaced by empty quotes within $a[0], which leaves ?B? to be returned.

 

Etc..

 

Hopefully that helps.

 

Cheers