Regular expression to check if two first words are same

Question

For example:

$s1 = \"Test Test the rest of string\"
$s2 = \"Test the rest of string\"

I would like to match positively $s1 but

Answer 1

This does not cause Test Testx to return true.

$string = "Test Test";

preg_match('/^(\w+)\s+\1(\b|$)/', $string);