PHP array_change_key_case() Function
Quick summary: The PHP array_change_key_case() function returns an array with all keys from array changed to lowercase or uppercase.
PHP array_change_key_case() Syntax
array_change_key_case(array $array, int $case = CASE_LOWER): arrayPHP
PHP array_change_key_case() Basic examples
$array = ['Name' => 'John', 'AGE' => 30];
print_r(array_change_key_case($array, CASE_LOWER));PHP
Output:
Array ( [name] => John [age] => 30 )Changes all keys to lowercase.
print_r(array_change_key_case($array, CASE_UPPER));PHP
Output:
Array ( [NAME] => John [AGE] => 30 )Changes all keys to uppercase.
PHP array_change_key_case() Real-world usage
$headers = ['Content-Type'=>'json'];
$normalized = array_change_key_case($headers, CASE_LOWER);
echo $normalized['content-type'];PHP
Output:
jsonNormalize header keys for consistent access.
PHP array_change_key_case() Edge cases
$array = ['A'=>1,'a'=>2];
print_r(array_change_key_case($array, CASE_LOWER));PHP
Output:
Array ( [a] => 2 )Duplicate keys may overwrite each other.
PHP array_change_key_case() Common mistakes
Expecting nested arrays to change
Only top-level keys are affected.
Incorrect
array_change_key_case(['User'=>['Name'=>'John']], CASE_LOWER);Correct
// manually apply recursively if neededFunction does not operate recursively.
PHP array_change_key_case() Frequently Asked Questions
What does array_change_key_case() do?
Changes all keys in an array to lower or upper case.
Default behavior?
Lowercase keys.
Use case?
Normalizing array keys.
Does it affect values?
No.
Handles nested arrays?
No.
Common mistake?
Expecting deep conversion.
Performance?
Fast.
Alternative?
Manual loop.
Return type?
Array.
Safe?
Yes.
Supports constants?
CASE_LOWER or CASE_UPPER.
Best practice?
Use for API normalization.