/**
* finds the longest common substring for the two provided strings
* @param string $a
* @param string $b
* @return string the longest common substring
*/
public static function longest_common_substring($a, $b)
{
$achars = preg_split('//u', $a, -1, PREG_SPLIT_NO_EMPTY);
$bchars = preg_split('//u', $b, -1, PREG_SPLIT_NO_EMPTY);
$arr = StringDiff::longest_common_subarray($achars, $bchars);
return implode($arr);
}
