common_paths.php

<?php

$paths = array(
    "/new/space/afsdfadsfthe_space_name/status/json",
    "/vagrant/public/space/afsdfadsfthe_space_name/index.php"
);

echo get_common_path($paths[0], $paths[1]);

// this is not yet
function get_common_path($path1, $path2) {

    // in the future the function should accept an array of paths,
    // as of now if more than two paths are provided, this will fail
    // because any common path elements which exist in the other arrays
    // are considered 'common' but only those elements that next to the
    // other without hole in the array are the real common elements.
    $paths = array($path1, $path2);

    $exploded_paths = array();
    foreach ($paths as $path) {
        $exploded_paths[] = explode('/', trim($path, '/'));
    }

    // initialize the common paths array
    $common_path = $exploded_paths[0];

    foreach ($exploded_paths as $path) {
        $common_path = array_intersect($path, $common_path);
    }

    return '/' . join('/', $common_path);
}