How to Use “array_intersect_key()” Function in PHP

In PHP, arrays are basic data structures for storing and managing sets of values. To perform different operations on arrays, PHP has a variety of array functions that are already integrated into compilers. Among one them is the “array_intersect_key()” function, which makes array comparisons based on keys.

This article will explore the “array_intersect_key()” function in PHP.

What is “array_intersect_key()” in PHP?

In PHP, the “array_intersect_key()” is a predefined function that accepts multiple arrays as inputs and produces an array containing every key-value pair that exists in the input arrays. Instead of comparing the arrays’ values, it compares their keys to find the intersection.

Syntax

The array_intersect_key() function basic syntax is as outlined below:

array array_intersect_key($array1, $array2,...)

Parameter: The “array_intersect_key()” function requires a minimum of two array arguments. Any number of arrays larger than others can be used, as long as they are separated by commas(,) sign.

Return Value: It returns key-value pairs of an array that are present in each of the arrays used as input. Upon receiving no matching keys, it returns the NULL array.

Key-based Comparison in “array_intersect_key()” Function

Strings and integers are two different data types that can be used as array keys in PHP. The “array_intersect_key()” function matches the keys by applying string equality tests, which require that the key’s type and associated value match for there to be a connection.

Then, the “array_intersect_key()” function uses the keys of the initial array (array1) as a reference when comparing keys. It determines whether the remaining arrays, such as array2, array3, and more have these keys. The relevant key-value combination will appear in the resulting array if a key is present in each of the arrays.

Example

In the below code, first, we initialize three arrays “$array1”, “$array2”, and “$array3” having the “my_name”,”my-age”, and “subject” keys along with the values. After that, these key values are compared using the “array_intersect_key()” function. It notes that the keys “my_name” and “my_age” are shared by all three arrays. The key-value pairs related to those common keys are contained in the “$total_result” variable. Lastly, revoke the “print_r()” method to show the items inside the “$total_result” variable:

<?php

$array1 = ['my_name' => 'Anne', 'my_age' => 24, 'Subject' => 'Computer'];

$array2 = ['my_name' => 'Anne', 'my_age' => 30, 'Class' => 'English'];

$array3 = ['my_name' => 'Hazal', 'my_age' => 24, 'Subject' => 'Computer'];

$total_result = array_intersect_key($array1, $array2, $array3);

print_r($total_result);

?>

Output

Key Points

The “array_intersect_key()” function matches the arrays according to their keys rather than their values.
All input arrays’ shared key-value pairs are contained in the resultant array.
A blank array is presented if no similar keys are discovered.

We have briefly described the “array_intersect_key()” function in PHP.

Conclusion

In PHP, the “array_intersect_key()” function is a useful function that compares arrays depending on their keys. When users need to locate common key-value pairs among several arrays, it is quite helpful. In this guide, we have illustrated the “array_intersect_key()” function in PHP.