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<?php $automerken = array("bmw" => "1 Series", "Mercedes" => "A klasse"); var_dump($automerken); print_r(array_change_key_case($automerken, CASE_UPPER)); print_r(array_change_key_case($automerken, CASE_LOWER));
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
array(2) { ["bmw"]=> string(8) "1 Series" ["Mercedes"]=> string(8) "A klasse" } Array ( [BMW] => 1 Series [MERCEDES] => A klasse ) Array ( [bmw] => 1 Series [mercedes] => A klasse )

preferences:
254.87 ms | 406 KiB | 370 Q