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<?php // Surprise surprise! When the 2nd array param of array_diff() contains an elemant with value false, // the result will no longer contain null values. class foo { } //hio function myIsset($value) { return isset($value); } $array1 = array( 'null1' => null, 'null2' => null, 'bool' => true, ); $filtered_array1 = array_filter($array1, 'myIsset'); var_dump($array1, $filtered_array1, array_diff($array1, $filtered_array1)); $array2 = $array1; $array2['bool'] = false; $filtered_array2 = array_filter($array2, 'myIsset'); var_dump($array2, $filtered_array2, array_diff($array2, $filtered_array2));
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 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 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 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
array(3) { ["null1"]=> NULL ["null2"]=> NULL ["bool"]=> bool(true) } array(1) { ["bool"]=> bool(true) } array(2) { ["null1"]=> NULL ["null2"]=> NULL } array(3) { ["null1"]=> NULL ["null2"]=> NULL ["bool"]=> bool(false) } array(1) { ["bool"]=> bool(false) } array(0) { }

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