Finding matching portions of two strings in PHP

Question

I'm looking for a simple way to find matching portions of two strings in PHP (specifically in the context of a URI)

For example, consider the two strings:

http://2.2.2.2/~machinehost/deployment_folder/

and

/~machinehost/deployment_folder/users/bob/settings

What I need is to chop off the matching portion of these two strings from the second string, resulting in:

users/bob/settings

before appending the first string as a prefix, forming an absolute URI.

Is there some simple way (in PHP) to compare two arbitrary strings for matching substrings within them?

EDIT: as pointed out, I meant the longest matching substring common to both strings

Answer 1

Assuming your strings are $a and $b, respectively, you can use this:

$a = 'http://2.2.2.2/~machinehost/deployment_folder/';
$b = '/~machinehost/deployment_folder/users/bob/settings';

$len_a = strlen($a);
$len_b = strlen($b);

for ($p = max(0, $len_a - $len_b); $p < $len_b; $p++)
    if (substr($a, $len_a - ($len_b - $p)) == substr($b, 0, $len_b - $p))
        break;

$result = $a.substr($b, $len_b - $p);

echo $result;

This result is http://2.2.2.2/~machinehost/deployment_folder/users/bob/settings.