php - how to replace group of texts in a link -

i have regex detects type of link.the detection part works fine replacing part dosen't work.i tried replace on http://regex101.com/

the code:

$link="cover_photos_s/yasinallana1984751717_post_notif_aurora_kuenzli_big.jpg";  //regex $reg_for_key="~((cover_photos_s\/)([a-za-z0-9]+)(_post_notif_)(\w+)(.[a-z]+))~i";  if(preg_match_all($reg_for_key,$link)) { //the replace string goes here } 

i need replace _post_notif_ in src _thumb_ .how do it?

solved thnx @onlinecop

in below regex, replace second captured group _thumb_,

^(cover_photos_s\/[a-z0-9a-z]+)(_\w+?_\w+?_)(.*)$ 

demo

your php code be,

<?php $link = "cover_photos_s/yasinallana1984751717_post_notif_aurora_kuenzli_big.jpg"; $reg_for_key = "~^(cover_photos_s\/[a-z0-9a-z]+)(_\w+?_\w+?_)(.*)$~"; $replacement = "$1_thumb_$3"; echo preg_replace($reg_for_key, $replacement, $link); ?>  //=> cover_photos_s/yasinallana1984751717_thumb_aurora_kuenzli_big.jpg 

ideone

explanation:

• (cover_photos_s\/[a-z0-9a-z]+) captures upto _ present before string post.
• (_\w+?_\w+?_) underscore, matches shortest word characters upto first underscore, matches string _post. again matches upto string notif because of ? operator after + symbol makes regex engine match shortest possibility plus following _ symbol. in turn regex engine capture second group of characters.
• all characters next them captured third group.
• in replacement part, replacing second group string give desired output.