Appending Arrays Without Altering Keys in PHP

Appending one array to another without affecting their keys is essential when you want to combine data while preserving existing indexes. In PHP, several options are available for this task, including array_merge.

Consider the following example:

$a = array('a', 'b');
$b = array('c', 'd');

We want to combine these arrays to get the following desired output:

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

Traditional Method

One way to achieve this is using a foreach loop:

foreach ($b AS $var) {
    $a[] = $var;
}

This method has a drawback: it can be tedious to manually loop through and append elements.

Elegant Solution: array_merge

PHP provides a built-in function called array_merge specifically designed for merging arrays:

$merge = array_merge($a, $b);

When we run this code, $merge will contain the desired result:

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

Avoid the Operator

While array_merge is the preferred option for appending arrays, it's worth noting that the operator should be avoided for this purpose.

$merge = $a   $b;

This operation will not actually merge the arrays. Instead, it will simply overwrite any duplicate keys in $a with the corresponding values from $b.