Understanding PHP's array_intersect() Function: Syntax, Parameters, Return Values, and Practical Examples

Syntax

array_intersect(array1, array2, ...)

The function compares two or more arrays and returns a new array containing all values that are present in every array passed as arguments.

Parameters

array1

, array2, etc., are the arrays to be compared; you may pass any number of arrays.

Return Value

array_intersect()

returns a new array with the intersecting values. If there is no intersection, an empty array is returned.

Parameter Requirements

All values in the arrays must be strings, integers, floats, or booleans; objects, resources, or other types are not allowed.

If an array contains duplicate values, the result will contain only a single instance of each intersecting value.

The original keys of the arrays are preserved in the result.

Examples

Example 1

$array1 = [1, 2, 3, 4, 5];
$array2 = [3, 4, 5, 6, 7];
$result = array_intersect($array1, $array2);
print_r($result);

Output:

Array
(
    [2] => 3
    [3] => 4
    [4] => 5
)

The two arrays share the values 3, 4, and 5, which are returned in the new array.

Example 2

$array1 = ['apple', 'banana', 'orange'];
$array2 = ['banana', 'grape', 'kiwi'];
$result = array_intersect($array1, $array2);
print_r($result);

Output:

Array
(
    [1] => banana
)

Only the value 'banana' is common to both arrays, so the result contains just that element.

Example 3

$array1 = [1, 2, 3, 4, 5];
$array2 = [6, 7, 8, 9, 10];
$result = array_intersect($array1, $array2);
print_r($result);

Output:

Array
(
)

Since the arrays have no common values, array_intersect() returns an empty array.

Notes

The number of arrays passed to array_intersect() is unlimited; the function will compare all of them.

The order of elements in the input arrays does not affect the result; only the values matter.

Summary

This article provides a comprehensive guide to PHP's array_intersect() function, illustrating its syntax, parameter rules, return behavior, and practical usage through multiple examples. By using this function, developers can efficiently compare arrays and extract their common elements, simplifying code and improving performance.

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