Array Example Name Result $a + $b Union Union of $a and $b. $a == $b Equality &true; if $a and $b have the same key/value pairs. $a === $b Identity &true; if $a and $b have the same key/value pairs in the same order and of the same types. $a != $b Inequality &true; if $a is not equal to $b. $a <> $b Inequality &true; if $a is not equal to $b. $a !== $b Non-identity &true; if $a is not identical to $b. The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored. "apple", "b" => "banana"); $b = array("a" => "pear", "b" => "strawberry", "c" => "cherry"); $c = $a + $b; // Union of $a and $b echo "Union of \$a and \$b: \n"; var_dump($c); $c = $b + $a; // Union of $b and $a echo "Union of \$b and \$a: \n"; var_dump($c); $a += $b; // Union of $a += $b is $a and $b echo "Union of \$a += \$b: \n"; var_dump($a); ?> ]]> &example.outputs; string(5) "apple" ["b"]=> string(6) "banana" ["c"]=> string(6) "cherry" } Union of $b and $a: array(3) { ["a"]=> string(4) "pear" ["b"]=> string(10) "strawberry" ["c"]=> string(6) "cherry" } Union of $a += $b: array(3) { ["a"]=> string(5) "apple" ["b"]=> string(6) "banana" ["c"]=> string(6) "cherry" } ]]> Elements of arrays are equal for the comparison if they have the same key and value. "banana", "0" => "apple"); var_dump($a == $b); // bool(true) var_dump($a === $b); // bool(false) ?> ]]> &reftitle.seealso; Array type Array functions