How to merge arrays and preserve the keys in PHP ?

Arrays in PHP are created using array() function. Arrays are variable that can hold more than one values at a time. There are three types of arrays:

1. Indexed Arrays
2. Associative Arrays
3. Multidimensional Arrays

Each and every value in an array has a name or identity attached to it used to access that element called keys.

To merge the two arrays array_merge() function works fine but it does not preserve the keys. Instead array_replace() function helps to merge two arrays while preserving their key.

Program 1: This example using array_replace() function to merge two arrays and preserve the keys.

Array
(
    [1] => Welcome
    [2] => To
    [3] => Geeks
    [4] => For
    [5] => Geeks
)

Program 1: This example using array_replace_recursive() function to merge two arrays and preserve the keys.

Array
(
    [1] => Welcome
    [2] => To
    [3] => Geeks
    [4] => For
    [5] => Geeks
)