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PHP array_uintersect Function

last modified March 13, 2025

The PHP array_uintersect function computes the intersection of arrays using a callback function for comparison. It's useful for custom comparison logic.

Basic Definition

The array_uintersect function compares array values using a callback. It returns an array containing all values present in all arguments.

Syntax: array_uintersect(array $array1, array $array2, ..., callable $value_compare_func): array. The callback must return an integer less than, equal to, or greater than zero.

Basic array_uintersect Example

This shows simple intersection of arrays with case-insensitive comparison.

basic_array_uintersect.php 
<?php

declare(strict_types=1);

$array1 = ["Apple", "Banana", "Cherry"];
$array2 = ["apple", "banana", "grape"];

$result = array_uintersect($array1, $array2, 'strcasecmp');

print_r($result);

This finds common elements ignoring case. The strcasecmp callback performs case-insensitive comparison. Both "Apple" and "Banana" match.

Custom Object Comparison

Compare arrays of objects using a custom property for intersection.

object_comparison.php 
<?php

declare(strict_types=1);

class Product {
    public function __construct(
        public string $name,
        public float $price
    ) {}
}

$products1 = [
    new Product("Laptop", 999.99),
    new Product("Phone", 699.99)
];

$products2 = [
    new Product("Laptop", 899.99),
    new Product("Tablet", 399.99)
];

$result = array_uintersect($products1, $products2, 
    fn($a, $b) => strcmp($a->name, $b->name));

print_r($result);

This finds products with matching names, ignoring price differences. The callback compares the name of each Product object.

Multiple Array Intersection

Find common elements across three arrays with custom comparison.

multiple_arrays.php 
<?php

declare(strict_types=1);

$array1 = [10, 20, 30, 40];
$array2 = [15, 20, 25, 30];
$array3 = [20, 30, 35, 40];

$result = array_uintersect($array1, $array2, $array3,
    fn($a, $b) => $a <=> $b);

print_r($result);

This finds numbers present in all three arrays. The spaceship operator callback performs standard numeric comparison. Only 20 and 30 match.

Complex Value Comparison

Use complex logic to compare array elements for intersection.

complex_comparison.php 
<?php

declare(strict_types=1);

function compareLength($a, $b): int {
    return strlen($a) <=> strlen($b);
}

$array1 = ["apple", "banana", "cherry"];
$array2 = ["pear", "kiwi", "orange"];

$result = array_uintersect($array1, $array2, 'compareLength');

print_r($result);

This finds strings with matching lengths across arrays. The callback compares string lengths rather than values. "apple" (5) matches "pear" (4) +1 diff.

Case-Sensitive String Comparison

Perform exact string matching with case sensitivity.

case_sensitive.php 
<?php

declare(strict_types=1);

$array1 = ["PHP", "Python", "Java"];
$array2 = ["php", "python", "ruby"];

$result = array_uintersect($array1, $array2, 'strcmp');

print_r($result);

This shows strict case-sensitive comparison. The strcmp callback matches exact strings. No matches found due to case differences.

Best Practices

  • Consistent Callbacks: Ensure callback returns proper comparison values.
  • Type Safety: Add type hints for robust comparison logic.
  • Performance: Sort arrays first for large datasets.
  • Readability: Use named functions for complex comparisons.

Source

PHP array_uintersect Documentation

This tutorial covered the PHP array_uintersect function with practical examples showing custom array intersection scenarios.

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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