PHP append one array to another (not array_push or +)

array_merge is the elegant way:

$a = array('a', 'b');
$b = array('c', 'd');
$merge = array_merge($a, $b); 
// $merge is now equals to array('a','b','c','d');

Doing something like:

$merge = $a + $b;
// $merge now equals array('a','b')

Will not work, because the + operator does not actually merge them. If they $a has the same keys as $b, it won't do anything.

It's a pretty old post, but I want to add something about appending one array to another:

If

• one or both arrays have associative keys
• the keys of both arrays don't matter

you can use array functions like this:

array_merge(array_values($array), array_values($appendArray));

array_merge doesn't merge numeric keys so it appends all values of $appendArray. While using native php functions instead of a foreach-loop, it should be faster on arrays with a lot of elements.

Addition 2019-12-13: Since PHP 7.4, there is the possibility to append or prepend arrays the Array Spread Operator way:

    $a = [3, 4];
    $b = [1, 2, ...$a];

As before, keys can be an issue with this new feature:

    $a = ['a' => 3, 'b' => 4];
    $b = ['c' => 1, 'a' => 2, ...$a];

"Fatal error: Uncaught Error: Cannot unpack array with string keys"

    $a = [3 => 3, 4 => 4];
    $b = [1 => 1, 4 => 2, ...$a];

array(4) { [1]=> int(1) [4]=> int(2) [5]=> int(3) [6]=> int(4) }

    $a = [1 => 1, 2 => 2];
    $b = [...$a, 3 => 3, 1 => 4];

array(3) { [0]=> int(1) [1]=> int(4) [3]=> int(3) }

Another way to do this in PHP 5.6+ would be to use the ... token

$a = array('a', 'b');
$b = array('c', 'd');

array_push($a, ...$b);

// $a is now equals to array('a','b','c','d');

This will also work with any Traversable

$a = array('a', 'b');
$b = new ArrayIterator(array('c', 'd'));

array_push($a, ...$b);

// $a is now equals to array('a','b','c','d');

A warning though:

• in PHP versions before 7.3 this will cause a fatal error if $b is an empty array or not traversable e.g. not an array
• in PHP 7.3 a warning will be raised if $b is not traversable

Why not use

$appended = array_merge($a,$b); 

Why don't you want to use this, the correct, built-in method.