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<?php $test = array( array('a' => 'testA', 'b' => 'testB'), array('a' =>'testC', 'b' => 'testD') ); print_r(array_keys('testC'));
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, string given in /in/lZXe0:9 Stack trace: #0 /in/lZXe0(9): array_keys('testC') #1 {main} thrown in /in/lZXe0 on line 9
Process exited with code 255.
Output for 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 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33
Warning: array_keys() expects parameter 1 to be array, string given in /in/lZXe0 on line 9
Output for 4.3.2 - 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
Warning: array_keys(): The first argument should be an array in /in/lZXe0 on line 9
Output for 4.3.0 - 4.3.1
Warning: array_keys() [http://www.php.net/function.array-keys]: The first argument should be an array in /in/lZXe0 on line 9

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