Trying to replace parts of string start with same search chars

Question

I\'m trying to replace parts of my string. But I met a problem when my search string start with same character:

$string = \"Good one :y. Keep going :y2\"; 

         


        

Answer 1

:y\b

Use this to replace only :y and not :y2.See demo.

https://regex101.com/r/sJ9gM7/9

$re = "":y\\b"m";
$str = "Good one :y. Keep going :y2\n";
$subst = "a";


$result = preg_replace($re, $subst, $str);

Similarly for :y2 use :y2\b.