The array_combine() function in PHP is used to create a new array by combining two arrays: one for keys and one for values. This function is particularly useful when you have two separate arrays that you want to merge into a single associative array, where one array contains the keys and the other contains the corresponding values.

Syntax:

array_combine(array $keys, array $values): array

Parameters:

• $keys: An array of keys. This array must contain unique values, as duplicate keys will result in an error.
• $values: An array of values that correspond to the keys. This array must have the same number of elements as the keys array; otherwise, the function will return false.

Return Value:

• The function returns a new associative array where each key from the $keys array is paired with the corresponding value from the $values array. If the input arrays do not have the same number of elements or if the keys array contains duplicate keys, it returns false.

Example 1: Basic Usage

Here’s a simple example demonstrating how to use array_combine():

<?php
$keys = ['a', 'b', 'c'];
$values = [1, 2, 3];

// Combine the arrays
$combined = array_combine($keys, $values);
print_r($combined);
?>

Output:

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

In this example, the keys array is combined with the values array to create an associative array.

Example 2: Different Lengths

If the $keys and $values arrays have different lengths, the function will return false.

<?php
$keys = ['a', 'b', 'c'];
$values = [1, 2]; // Fewer values than keys

// Attempt to combine the arrays
$result = array_combine($keys, $values);

if ($result === false) {
    echo "Error: The arrays must have the same number of elements.";
}
?>

Output:

Error: The arrays must have the same number of elements.

Example 3: Duplicate Keys

If the $keys array contains duplicate values, an error will occur.

<?php
$keys = ['a', 'b', 'a']; // Duplicate key 'a'
$values = [1, 2, 3];

// Attempt to combine the arrays
$result = array_combine($keys, $values);

if ($result === false) {
    echo "Error: Keys must be unique.";
}
?>

Output:

Error: Keys must be unique.

Example 4: Using Numeric Keys

You can also use numeric keys with array_combine().

<?php
$keys = [0, 1, 2];
$values = ['first', 'second', 'third'];

// Combine the arrays
$combined = array_combine($keys, $values);
print_r($combined);
?>

Output:

Array
(
    [0] => first
    [1] => second
    [2] => third
)

Practical Usage:

• The array_combine() function is useful in various scenarios, such as:
  • Creating associative arrays from two separate datasets.
  • Merging data from different sources where keys and values are provided separately.
  • Preparing structured data for further processing or output.

Summary:

• array_combine($keys, $values) creates a new associative array from two input arrays: one for keys and one for values.
• The function requires both input arrays to have the same number of elements and ensures that keys are unique.
• It simplifies the process of transforming two separate lists into a structured associative array, making data handling more efficient in PHP applications.