在两个单词之间提取一个字符串

Question

I want to extract hash from string below which is e5e1af55bad959546ec7608cc8685fe67bc5426e

$word1 = 'btih:';
$word2 = '&dn';
$magnet = "[magnet:?xt=urn:btih:e5e1af55bad959546ec7608cc8685fe67bc5426e&dn=The+Deadly+Game+2013+DVDRip+XviD-EVO+&tr=udp%3A%2F%2Ftracker.openbittorrent.com%3A80&tr=udp%3A%2F%2Ftracker.publicbt.com%3A80&tr=udp%3A%2F%2Ftracker.istole.it%3A6969&tr=udp%3A%2F%2Ftracker.ccc.de%3A80&tr=udp%3A%2F%2Fopen.demonii.com%3A1337]";
if(preg_match('/'.preg_quote($word1).'(.*?)'.preg_quote($word2).'/is', $magnet, $match)){
$upper = strtoupper($match['1']);
$generated = "http://torrage.com/torrent/".$upper.".torrent";
}

in above code, the hash are located between btih: and &dn can i know why my code doesnt work?

Answer 1

You can use this lookaround based regex:

'/(?<=btih:)(.+?)(?=&dn=)/'

This means capture a string which is preceded by bith: and followed by &dn=

Alternatively you can avoid lookbehind and use:

'/:btih:\K(.+?)(?=&dn=)/'

Here \K is used to reset matched pattern.

As an another alternative you can avoid lookahead also and use:

'/:btih:(.+?)&dn=/'

And use matched group #1