Understanding and Using PHP's array_merge() Function

What is array_merge() function?

array_merge() is a PHP function that merges one or more arrays into a new array, preserving order and returning the combined result.

Usage of array_merge()

Function syntax:

array array_merge ( array $array1 [, array $... ] )

Examples:

(1) Merge two arrays

$array1 = array("red", "green");
$array2 = array("blue", "yellow");
$result = array_merge($array1, $array2);
// Output: Array ( [0] => red [1] => green [2] => blue [3] => yellow )

(2) Merge multiple arrays

$array1 = array("red", "green");
$array2 = array("blue", "yellow");
$array3 = array("orange", "purple");
$result = array_merge($array1, $array2, $array3);
// Output: Array ( [0] => red [1] => green [2] => blue [3] => yellow [4] => orange [5] => purple )

Note: When arrays have identical keys, later arrays overwrite earlier values.

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
// Output: Array ( [color] => green [0] => 2 [1] => 4 [2] => a [3] => b [shape] => trapezoid [4] => 4 )

Summary

array_merge() is a practical PHP function for merging arrays; it combines one or more arrays into a new one, with later values overriding earlier ones for duplicate keys.