PHP 8 reference · Array Functions

PHP array_merge() Function

Merge one or more arrays into a new array. Numeric keys are renumbered; for string keys the later value wins.

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Syntax

array_merge(array ...$arrays): array

Parameter	Description
`arrays`	The arrays to merge.

A new merged array.

Join listsTry it yourself

<?php
print_r(array_merge(["a", "b"], ["c"], ["d", "e"]));

Output

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)

Override defaultsTry it yourself

<?php
$defaults = ["color" => "blue", "size" => "M"];
$chosen = ["size" => "L"];
print_r(array_merge($defaults, $chosen));

Output

Array
(
    [color] => blue
    [size] => L
)

array_merge() vs +Try it yourself

<?php
print_r(array_merge([5 => "a"], [5 => "b"])); // renumbered
print_r([5 => "a"] + [5 => "b"]);             // + keeps the first

Output

Array
(
    [0] => a
    [1] => b
)
Array
(
    [5] => a
)

Integer keys are renumbered, so IDs used as keys are lost. Use $a + $b or array_replace() to keep them.
Merging inside a loop ($all = array_merge($all, $chunk)) is slow; collect chunks and call array_merge(...$chunks) once.

Version	Change
PHP 4.0	Added
PHP 7.4	Can be called with no arguments (returns `[]`).

array_merge_recursive() · Merge arrays and, when string keys clash, combine their values into arrays instead of overwriting.
array_replace() · Replace values of the first array with values that have the same keys in later arrays. Numeric keys are kept.
array_combine() · Create an array by using one array for keys and another for values. Both arrays must have the same number of elements.
array_push() · Add one or more elements to the end of an array and return its new length. $array[] = $value does the same for one value.
PHP Arrays · tutorial
PHP Array Functions · tutorial

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