<?php

$a=array('a','b','c');
$b=array('b','c','b');
var_dump(array_merge($a,$b));

array(6) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "b"
  [4]=>
  string(1) "c"
  [5]=>
  string(1) "b"
}