preg_grep() returns the array consisting of the elements of the input array that match the given pattern.
flags can be the following flag:
If this flag is passed, preg_grep() returns the elements of the input array that do not match the given pattern. This flag is available since PHP 4.2.0.
Since PHP 4.0.4, the results returned by preg_grep() are indexed using the keys from the input array. If this behavior is undesirable, use array_values() on the array returned by preg_grep() to reindex the values.