An algorithm problem in php

An algorithm of php has such an array.
$ Arr = array (
Array ('a _ 1', 'a _ 2 '),
Array ('B _ 1',' B _ 2 '),
Array ('c _ 1', 'c _ 2 ')
);
It can be calculated as follows.
Array (
'A _ 1, B _1, c_1 ',
'A _ 1, B _1, c_2 ',
'A _ 1, B _2, c_1 ',
'A _ 1, B _2, c_2 ',
'A _ 2, B _1, c_1 ',
'A _ 2, B _1, c_2 ',
'A _ 2, B _2, c_1 ',
'A _ 2, B _2, c_2 ',
);
It is to combine each element in the array with other elements.

Reply to discussion (solution)

function foo($d) {  $r = array_pop($d);  while($d) {    $t = array();    $s = array_pop($d);    if(! is_array($s)) $s = array($s);    foreach($s as $x) {      foreach($r as $y) $t[] = array_merge(array($x), is_array($y) ? $y : array($y));    }    $r = $t;  }  return $r;}$ary = array(    'a'=>array('a_1','a_2'),    'b'=>array('b_1','b_2'),    'c'=>array('c_1','c_2'),);print_r(foo($ary));

Array(    [0] => Array        (            [0] => a_1            [1] => b_1            [2] => c_1        )    [1] => Array        (            [0] => a_1            [1] => b_1            [2] => c_2        )    [2] => Array        (            [0] => a_1            [1] => b_2            [2] => c_1        )    [3] => Array        (            [0] => a_1            [1] => b_2            [2] => c_2        )    [4] => Array        (            [0] => a_2            [1] => b_1            [2] => c_1        )    [5] => Array        (            [0] => a_2            [1] => b_1            [2] => c_2        )    [6] => Array        (            [0] => a_2            [1] => b_2            [2] => c_1        )    [7] => Array        (            [0] => a_2            [1] => b_2            [2] => c_2        ))

Thank you. what is the name of this algorithm?

It is called Cartesian product.