preg_match_all with callback?

You want preg_replace_callback().

You would match them with a regex like /=\d+?;/ and then your callback would look like...

function($matches) { return dechex($matches[1]); }

Combined, it gives us...

preg_replace_callback('/=(\d+?);/', function($matches) { 
   return dechex($matches[1]);
}, $str);

CodePad.

Alternatively, you could use positive lookbehind/forward to match the delimiters and then pass 'dechex' straight as the callback.

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