PHP array_merge: Combine Multiple Arrays into One

You have two or more arrays. You want one. That is the problem array_merge solves in PHP. This function lets you combine arrays into one result. You use it when you need a clean and full merge.

Understand the array_merge Function in PHP

array_merge puts arrays together. It adds values from one into another. If both arrays use the same keys, it picks values from the last one. You get a single array as output.

Here is the syntax:

array_merge($array1,$array2, ...$arrays)

• You must pass at least one array.
• You can pass more arrays if you want.
• The function adds values in order.

It returns one array. That array holds all values from the input arrays. If it sees repeated string keys, it keeps the one from the last array.

For example:

$first = ['PHP', 'JS'];
$second = ['PYTHON', 'C#'];
$langs = array_merge($first, $second);
print_r($langs);

Output:

Array
(
    [0] => PHP
    [1] => JS
    [2] => PYTHON
    [3] => C#
)

Each array adds its values to the final result and indexes reset from zero.

If both arrays use numbers as keys, PHP throws them out and starts from zero again. The order stays, but the indexes change.

$a = [3 => 'x', 4 => 'y'];
$b = [7 => 'z'];
$result = array_merge($a, $b);
print_r($result);

Output:

Array
(
    [0] => x
    [1] => y
    [2] => z
)

You see the same values. But the keys now go from 0 to 2.

If arrays use named keys, PHP keeps the last value it finds.

$a = ['type' => 'fruit', 'name' => 'apple'];
$b = ['name' => 'banana', 'color' => 'yellow'];
$result = array_merge($a, $b);
print_r($result);

Output:

Array
(
    [type] => fruit
    [name] => banana
    [color] => yellow
)

The key name appears in both arrays. The second one wins. Others stay untouched.

PHP array_merge Examples

Mixed arrays (indexed + associative): You can pass both types in one call. PHP adds all values and applies the same rules.

$first = ['a', 'b', 'c'];
$second = ['type' => 'letter', 1 => 'd'];
$result = array_merge($first, $second);
print_r($result);

Output:

Array
(
    [0] => a
    [1] => d
    [2] => c
    [type] => letter
)

Key 1 appears in both. The second one replaces the first. Named keys go in as-is.

Associative arrays: Only keys matter here. If both arrays use the same key, the second one overwrites the first.

$settingsA = ['mode' => 'dark', 'font' => 'Arial'];
$settingsB = ['font' => 'Verdana', 'size' => 12];
$finalSettings = array_merge($settingsA, $settingsB);
print_r($finalSettings);

You get the new font and keep the old mode.

Merging two indexed arrays: PHP drops the old keys and starts fresh.

$week1 = ['Mon', 'Tue'];
$week2 = ['Wed', 'Thu'];
$week = array_merge($week1, $week2);
print_r($week);

Output:

Array
(
    [0] => Mon
    [1] => Tue
    [2] => Wed
    [3] => Thu
)

It keeps the order. Keys reset to match that order.

Merging more than two arrays: You can pass three, four, or more arrays. PHP keeps going until it merges all.

$a = ['red', 'blue'];
$b = ['green'];
$c = ['yellow', 'black'];
$colors = array_merge($a, $b, $c);
print_r($colors);

Output:

Array
(
    [0] => red
    [1] => blue
    [2] => green
    [3] => yellow
    [4] => black
)

You can mix and match arrays. PHP keeps the order you pass them in.

Wrapping Up

In this article, you learn how array_merge works and how it treats different types of arrays. You see what happens with indexed arrays, with named keys, and when both types appear in one merge.

Here is a quick recap:

• It combines arrays in order.
• It resets numeric keys.
• It keeps the last value for each repeated named key.
• You can pass more than two arrays at once.

Thank you for reading. Here you will find more PHP tutorials.

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