php USES the preg_replace function to match images and link them

Description: preg_replace performs regular expression search and replacement, and it is recommended to use str_replace() if it is simply a matching string, because it is much more efficient.
mixed preg_replace ( mixed pattern, mixed replacement, mixed subject [, int limit])

Search subject for a match of the pattern pattern and replace it with replacement. If limit is specified, only limit matches are replaced; if limit is omitted or its value is -1, all matches are replaced.

As mentioned before, php matches the image in the article with preg_match_all. The code to match the image and add the link is given below:

<?php
$con = file_get_contents("https://www.ofstack.com/");
$pattern="/<[img|IMG].*?src=[\'|\"](.*?(?:[\.gif|\.jpg|\.png]))[\'|\"].*?[\/]?>/";
$new_con = preg_replace($pattern,"<a href='$1'>$0</a>",$con);
echo $new_con;
?> 

Description: $0 means the match content, $1 means the first () match content, $2 means the second () match content, and so on!
Add link to picture so, the friend that is interested in might as well test with one's own hands next.