<?php

$a = array(range(0,4), range(5,10));
print_r($a);
print_r(call_user_func_array('array_merge', $a));

Array
(
    [0] => Array
        (
            [0] => 0
            [1] => 1
            [2] => 2
            [3] => 3
            [4] => 4
        )

    [1] => Array
        (
            [0] => 5
            [1] => 6
            [2] => 7
            [3] => 8
            [4] => 9
            [5] => 10
        )

)
Array
(
    [0] => 0
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
    [6] => 6
    [7] => 7
    [8] => 8
    [9] => 9
    [10] => 10
)