PHP array_combine Function

last modified March 13, 2025

The PHP array_combine function creates an array by using one array for keys and another for values. It's useful for pairing related data.

Basic Definition

The array_combine function merges two arrays into an associative array. The first array provides keys, the second provides corresponding values.

Syntax: array_combine(array $keys, array $values): array. Both arrays must have equal number of elements. Returns new associative array.

Basic array_combine Example

This shows how to combine simple arrays of keys and values into an associative array.

basic_array_combine.php

<?php

$keys = ['name', 'age', 'city'];
$values = ['Alice', 25, 'New York'];

$combined = array_combine($keys, $values);

print_r($combined);

This combines string keys with mixed values. The resulting array uses $keys as keys and $values as corresponding values in the same order.

Combining Numeric Arrays

Demonstrates combining numeric arrays to create an associative array.

numeric_arrays.php

<?php

$ids = [101, 102, 103];
$names = ['Product A', 'Product B', 'Product C'];

$products = array_combine($ids, $names);

print_r($products);

Here numeric IDs become array keys paired with product names. Note that array keys can be integers in PHP associative arrays.

Error Handling

Shows what happens when arrays of different sizes are combined.

error_handling.php

<?php

$keys = ['a', 'b', 'c'];
$values = [1, 2];

try {
    $result = array_combine($keys, $values);
    print_r($result);
} catch (ValueError $e) {
    echo "Error: " . $e->getMessage();
    // Output: Error: array_combine(): Argument #2 ($values) must have the same number of elements as argument #1 ($keys)
}

The function throws a ValueError when array sizes differ. Always ensure arrays have equal length before combining them.

Combining with Array Functions

Demonstrates using array_combine with other array functions like array_map.

with_functions.php

<?php

$headers = ['ID', 'NAME', 'PRICE'];
$data = ['101', 'Widget', '19.99'];

// Convert headers to lowercase keys
$keys = array_map('strtolower', $headers);
$combined = array_combine($keys, $data);

print_r($combined);

This transforms headers to lowercase before combining. The array_map function modifies the keys array before it's used in array_combine.

Real-world CSV Example

Shows a practical example of processing CSV data into associative arrays.

csv_example.php

<?php

$csvData = [
    ['id', 'name', 'email'],
    [1, 'John Doe', 'john@example.com'],
    [2, 'Jane Smith', 'jane@example.com']
];

$headers = array_shift($csvData); // Get headers
$result = [];

foreach ($csvData as $row) {
    $result[] = array_combine($headers, $row);
}

print_r($result);

This processes CSV-like data into an array of associative arrays. Each row is combined with the headers to create meaningful key-value pairs.

Best Practices

Equal Length: Always verify arrays have same number of elements.
Valid Keys: Ensure keys are valid (strings or integers).
Data Alignment: Confirm values correspond to correct keys.
Error Handling: Use try-catch for production code.

Source

PHP array_combine Documentation

This tutorial covered the PHP array_combine function with practical examples showing its usage for creating associative arrays from separate keys and values arrays.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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