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PHP array_diff_ukey() Function

Quick summary: The PHP array_diff_ukey() function compares the keys of two (or more) arrays using a user-defined key comparison function, and returns the differences.

PHP array_diff_ukey() Syntax 

array_diff_ukey(array $array, array ...$arrays, callable $key_compare_func): array
PHP

PHP array_diff_ukey() Basic examples 

$a = ['a'=>1,'b'=>2];
$b = ['A'=>3];
$result = array_diff_ukey($a,$b,'strcasecmp');
print_r($result);
PHP
Output:
Array ( [b] => 2 )

Compares keys using a user-defined function.

PHP array_diff_ukey() Real-world usage 

function cmp($a,$b){ return strcmp($a,$b); }
$a=['id'=>1,'name'=>'John'];
$b=['id'=>2];
print_r(array_diff_ukey($a,$b,'cmp'));
PHP
Output:
Array ( [name] => John )

Find unmatched keys with custom logic.

PHP array_diff_ukey() Edge cases 

array_diff_ukey($a,$b,'not_existing_function');
PHP
Output:
Warning

Callback must exist and be callable.

PHP array_diff_ukey() Common mistakes

Confusing with array_diff_uassoc()

array_diff_ukey() compares keys only.

Incorrect
array_diff_ukey(['a'=>1],['a'=>2],'strcmp');
Correct
array_diff_uassoc(['a'=>1],['a'=>2],'strcmp');

Use correct function depending on comparison needs.

PHP array_diff_ukey() Frequently Asked Questions

What does array_diff_ukey() do?

Compares array keys using a user-defined function.

Use case?

Custom key filtering.

Callback required?

Yes.

Common mistake?

Wrong comparison logic.

Performance?

Slower than native.

Return type?

Array.

Safe?

Yes.

Alternative?

array_diff_key().

Value ignored?

Yes.

Key comparison flexible?

Yes.

Best practice?

Keep callback simple.

Used in custom logic?

Yes.

PHP array_diff_ukey() Related PHP Functions