PHP array_intersect_uassoc: How it Works with Examples

PHP array_intersect_uassoc checks two or more arrays and returns matches. It compares both the values and the keys with a custom callback function.

How the array_intersect_uassoc Works in PHP

PHP array_intersect_uassoc compares arrays and returns elements that exist in all arrays. It checks both keys and values.

The syntax looks like this:

array_intersect_uassoc(array $array1, array $array2, array ... , callable $callback)

Here is how it works:

• $array1: the main array to compare.
• $array2, ...: arrays to check against the main array.
• $callback: function that compares the keys.

The function returns an array with the matched values and the matched keys.

array_intersect_uassoc checks both the value and the key. The callback handles the key comparison. If the callback says the keys match, the value comparison decides the result.

Use this function when you need both the value and the key to match. It works well for associative arrays where the order or the key matters.

For a quick example:

$result = array_intersect_uassoc($array1, $array2, 'compareFunction');

The callback defines the key comparison rule. The function returns only elements that match in both value and key.

Examples of array_intersect_uassoc in PHP

Compare Arrays with String Keys:

function compareKeys($a, $b) {
    if ($a === $b) return 0;
    return ($a > $b) ? 1 : -1;
}

$array1 = ["a" => "red", "b" => "blue", "c" => "green"];
$array2 = ["a" => "red", "b" => "yellow", "d" => "green"];

$result = array_intersect_uassoc($array1, $array2, 'compareKeys');
print_r($result);

This example compares arrays with string keys. Only the key “a” with value “red” matches. The function checks both the key and the value.

Compare Arrays with Mixed Keys:

function compareKeys($a, $b) {
    return strcmp((string)$a, (string)$b);
}

$array1 = [1 => "apple", 2 => "banana", "x" => "pear"];
$array2 = ["1" => "apple", 2 => "banana", "y" => "pear"];

$result = array_intersect_uassoc($array1, $array2, 'compareKeys');
print_r($result);

This example compares numeric and string keys. The comparison function casts keys to strings. It returns the values with keys that match after the conversion.

Here is the outout:

Array
(
    [1] => apple
    [2] => banana
)

Advanced Comparison with Case Sensitivity:

function compareKeys($a, $b) {
    return strcmp($a, $b);
}

$array1 = ["A" => "dog", "B" => "cat"];
$array2 = ["a" => "dog", "B" => "cat"];

$result = array_intersect_uassoc($array1, $array2, 'compareKeys');
print_r($result);

This example shows case sensitivity in key comparison. The function does not match “A” with “a”. Only the key “B” with value “cat” appears in the result.

The output:

Array
(
    [B] => cat
)

Multiple Arrays with Custom Key Logic:

function compareKeys($a, $b) {
    return strcasecmp($a, $b);
}

$array1 = ["One" => 10, "Two" => 20, "Three" => 30];
$array2 = ["one" => 10, "Two" => 40, "Three" => 30];
$array3 = ["ONE" => 10, "Three" => 30, "Four" => 50];

$result = array_intersect_uassoc($array1, $array2, $array3, 'compareKeys');
print_r($result);

This example checks three arrays with case-insensitive keys. The function returns “One” with value 10 and “Three” with value 30.

The output:

Array
(
    [One] => 10
    [Three] => 30
)

Wrapping Up

You learned how array_intersect_uassoc works with keys and values. You also saw examples with string keys, mixed keys, case rules, and multiple arrays.

Here is a quick recap:

• It compares values and keys across arrays.
• It uses a custom callback for key comparison.
• It returns only matched pairs of keys and values.

FAQs

function compare_keys($a, $b) {
    if ($a === $b) {
        return 0;
    }
    return ($a > $b) ? 1 : -1;
}

$array1 = array("a" => "red", "b" => "green", "c" => "blue");
$array2 = array("a" => "red", "b" => "yellow", "d" => "blue");

$result = array_intersect_uassoc($array1, $array2, "compare_keys");
print_r($result);

function cmp($a, $b) {
    if ($a === $b) return 0;
    return ($a > $b) ? 1 : -1;
}

$a1 = array("x" => "car", "y" => "bus", "z" => "train");
$a2 = array("x" => "car", "y" => "bike", "z" => "train");
$a3 = array("x" => "car", "y" => "bus", "z" => "plane");

$result = array_intersect_uassoc($a1, $a2, $a3, "cmp");
print_r($result);

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