The `array_merge()` function in PHP is used to merge two or more arrays into a single array. It takes variable number of arguments, each of which is an array to be merged. The function returns a new array that contains all the elements from all the input arrays.

Syntax:

“`php
array_merge(array1, array2, …, arrayn)
“`

Parameters:

* array1, array2, …, arrayn: The arrays to be merged.

Example:

“`php
$array1 = array(“a”, “b”, “c”);
$array2 = array(“d”, “e”, “f”);

$merged_array = array_merge($array1, $array2);

print_r($merged_array);
“`

This will print the following output:

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

The `array_merge()` function can be used to merge arrays of different sizes and types. It will automatically convert the values to the appropriate type. For example, if you merge an array of strings with an array of integers, the resulting array will contain strings and integers.

The `array_merge()` function can also be used to merge associative arrays. In this case, the keys of the resulting array will be the union of the keys of all the input arrays. The values of the resulting array will be the values of the corresponding keys in the input arrays.

The `array_merge()` function is a powerful and versatile function that can be used to combine data from multiple arrays into a single array. It is a core function in PHP and is used in many applications.

Here are some of the common use cases of the `array_merge()` function:

* Combining data from multiple forms
* Creating a new array from multiple existing arrays
* Merging arrays of different sizes and types
* Merging associative arrays

The `array_merge()` function is a simple yet powerful function that can be used to solve a variety of data manipulation problems. It is a core function in PHP and is used in many applications.