php add array to array

If you have two arrays and you want to combine them into a single array

using array_merge( array1, array2 ,array3 ...) function

this function will return the array

Example 

<?php
    echo'<pre>';
    $array1    = [1,2,3];
    $array2    = ['a','b','c'];
    $array3    = ['d','e','f'];
    $array4    = array_merge($array1,$array2,$array3);
    print_r($array4);
    echo'</pre>';
?>

output 

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => a
    [4] => b
    [5] => c
    [6] => d
    [7] => e
    [8] => f
)