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PHP array_intersect() Function

Quick summary: The PHP array_intersect() function computes the intersection of arrays using values.

PHP array_intersect() Syntax 

array_intersect(array $array, array ...$arrays): array
PHP

PHP array_intersect() Basic examples 

var_dump(array_intersect([1,2,3], [2,3,4]));
PHP
Output:
array(2) {
  [1]=> int(2)
  [2]=> int(3)
}

Returns values common to both arrays.

PHP array_intersect() Real-world usage 

$userRoles = ['admin','editor'];
$allowed = ['editor','viewer'];
var_dump(array_intersect($userRoles, $allowed));
PHP
Output:
array(1) {
  [1]=> string(6) "editor"
}

Checks access permissions.

PHP array_intersect() Edge cases 

var_dump(array_intersect([], [1,2]));
PHP
Output:
array(0) {
}

Intersecting with an empty array returns an empty array.

PHP array_intersect() Common mistakes

Expecting reindexed keys

array_intersect preserves keys from the first array.

Incorrect
array_intersect([1,2,3],[2]);
Correct
array_values(array_intersect([1,2,3],[2]));

Reindex manually if needed.

PHP array_intersect() Frequently Asked Questions

What does array_intersect() do in PHP?

array_intersect() returns values present in all given arrays.

Does array_intersect() preserve keys?

Yes, it preserves keys from the first array.

Is array_intersect() case-sensitive?

Yes, comparisons are case-sensitive.

Does array_intersect() compare keys?

No, it compares only values.

Can array_intersect() handle multiple arrays?

Yes, it can compare more than two arrays.

Does array_intersect() modify arrays?

No, it returns a new array.

What is the difference from array_diff()?

array_intersect() finds common values, while array_diff() finds differences.

Can array_intersect() work with associative arrays?

Yes, but only values are compared.

What happens with duplicates?

Duplicates are preserved if present in the first array.

Is array_intersect() fast?

Performance depends on array size.

Use case of array_intersect()?

Finding common elements between datasets.

Can it be combined with array_map()?

Yes, often used together for data processing.

PHP array_intersect() Related PHP Functions