Array Operators
The only array operator in PHP is the + operator. It appends the right handed array to the left handed, whereas duplicated keys are NOT overwritten.
| $a = array("a" => "apple", "b" => "banana");
$b = array("a" =>"pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b;
 var_dump($c); | 
| array(3) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
  ["c"]=>
  string(6) "cherry"
 } | 
See also the manual sections on the Array type and Array functions.
