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PHP array_flip() Function

Quick summary: The PHP array_flip() function swaps keys and values in an array.

PHP array_flip() Syntax 

array_flip(array $array): array
PHP

PHP array_flip() Basic examples 

var_dump(array_flip(['a'=>1,'b'=>2]));
PHP
Output:
array(2) { [1]=> string(1) "a" [2]=> string(1) "b" }

Keys become values and values become keys.

PHP array_flip() Real-world usage 

$roles = ['admin'=>'A','editor'=>'E'];
var_dump(array_flip($roles));
PHP
Output:
array(2) { ["A"]=> string(5) "admin" ["E"]=> string(6) "editor" }

Creates reverse lookup tables.

PHP array_flip() Edge cases 

var_dump(array_flip(['a'=>1,'b'=>1]));
PHP
Output:
array(1) { [1]=> string(1) "b" }

Duplicate values overwrite previous keys.

PHP array_flip() Common mistakes

Flipping arrays with non-scalar values

Only scalar values can be flipped.

Incorrect
array_flip(['a'=>[1,2]]);
Correct
array_map('array_flip', [['a'=>1,'b'=>2]]);

Ensure values are scalar before flipping.

PHP array_flip() Frequently Asked Questions

What does array_flip() do?

Swaps keys with values in an array.

What happens with duplicate values?

Last value overwrites previous ones.

Does it modify array?

No.

Can values be arrays?

No, only strings and integers.

Use case?

Reversing mappings.

Performance?

Fast.

Handles associative arrays?

Yes.

Keys lost?

Original keys become values.

Supports objects?

No.

Maintains order?

Yes.

Edge cases?

Duplicate values.

Alternative?

Custom loop.

PHP array_flip() Related PHP Functions