--TEST-- Test array_key_exists() function : object functionality - different visibilities --FILE-- var1 = $a; $this->var2 = $b; if (!is_null($c)) { $this->var3 = $c; } } } echo "\n-- Do not assign a value to \$class1->var3 --\n"; $class1 = new myClass ('a', 'b'); echo "\$key = var1:\n"; var_dump(array_key_exists('var1', $class1)); echo "\$key = var2:\n"; var_dump(array_key_exists('var2', $class1)); echo "\$key = var3:\n"; var_dump(array_key_exists('var3', $class1)); echo "\$class1:\n"; var_dump($class1); echo "\n-- Assign a value to \$class2->var3 --\n"; $class2 = new myClass('x', 'y', 'z'); echo "\$key = var3:\n"; var_dump(array_key_exists('var3', $class2)); echo "\$class2:\n"; var_dump($class2); echo "Done"; ?> --EXPECTF-- *** Testing array_key_exists() : object functionality *** -- Do not assign a value to $class1->var3 -- $key = var1: bool(true) $key = var2: bool(false) $key = var3: bool(false) $class1: object(myClass)#1 (3) { ["var1"]=> string(1) "a" ["var2":protected]=> string(1) "b" ["var3":"myClass":private]=> NULL } -- Assign a value to $class2->var3 -- $key = var3: bool(false) $class2: object(myClass)#2 (3) { ["var1"]=> string(1) "x" ["var2":protected]=> string(1) "y" ["var3":"myClass":private]=> string(1) "z" } Done