Online PHP editor | output for 1WVGl

<?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. function myIsset($value) { return isset($value); } $arrayWithTrueValue = array( 'null1' => null, 'null2' => null, 'bool' => true, ); $filteredArray = array_filter($arrayWithTrueValue, 'myIsset'); var_dump($arrayWithTrueValue, $filteredArray, array_diff($arrayWithTrueValue, $filteredArray)); $arrayWithFalseValue = $arrayWithTrueValue; $arrayWithFalseValue['bool'] = false; $filteredArrayAlmostEmpty = array_filter($arrayWithFalseValue, 'myIsset'); var_dump($arrayWithFalseValue, $filteredArrayAlmostEmpty, array_diff($arrayWithFalseValue, $filteredArrayAlmostEmpty));