The preg_match_all() function matches all occurrences of pattern in string.
It will place these matches in the array pattern_array in the order you specify using the optional input parameter order. There are two possible types of order −
PREG_PATTERN_ORDER − is the default if the optional order parameter is not included. PREG_PATTERN_ORDER specifies the order in the way that you might think most logical; $pattern_array[0] is an array of all complete pattern matches, $pattern_array[1] is an array of all strings matching the first parenthesized regexp, and so on.