instanceof

 1 <?php
 2 /*
 3 instanceof is used to determine whether a PHP variable is an instantiated object of a certain class:
 4 */
 5 class MyClass
 6 {
 7 
 8 }
 9 
10 class NotMyClass
11 {
12 
13 }
14 
15 $a = new MyClass;
16 
17 var_dump($a instanceof MyClass);
18 var_dump($a instanceof NotMyClass);
19 // boolean true boolean false
20 /*
21 instanceof can also be used to determine whether a variable is an instantiated object of a class that inherits from a parent class:
22 */
23 
24 class ParentClass
25 {
26 
27 }
28 
29 class ChildClass extends ParentClass
30 {
31 
32 }
33 
34 $a = new ChildClass;
35 var_dump($a instanceof ChildClass);
36 var_dump($a instanceof ParentClass);
37 // true true
38 /*
39 Lastly, instanceof can also be used to determine whether a variable is an instantiated object of a class that implements an interface:
40 */
41 
42 interface MyInterface
43 {
44 
45 }
46 
47 class MyClass2 implements MyInterface
48 {
49 
50 }
51 
52 $a = new MyClass2;
53 
54 var_dump($a instanceof MyClass2 );
55 var_dump($a instanceof MyInterface);
56 // true true
57 
58 /*
59 Although instanceof is usually used with a literal classname, it can also be used with another object or a string variable:
60 */
61 
62 $b = new MyClass2;
63 $c = ‘MyClass2‘;
64 $d = ‘NotMyClass2‘;
65 
66 var_dump($a instanceof $b); //$b is an object of class MyClass
67 var_dump($a instanceof $c); //$c is a string ‘MyClass‘
68 var_dump($a instanceof $d); //$d is a string ‘NotMyClass‘
69 
70 //true true false
71 
72 $e = ‘MyClass2‘;
73 var_dump($e instanceof $c);
74 var_dump($c instanceof $e);
75 
76 //false false
77 
78 /*
79 instanceof does not throw any error if the variable being tested is not an object, it simply returns FALSE. Constants, however, are not allowed.
80 */
81 $a = 1;
82 $b = null;
83 $c = imagecreate(5,5);
84 var_dump($a instanceof stdClass);
85 var_dump($b instanceof stdClass);
86 var_dump($c instanceof stdClass);
87 // false false false
88 /*
89 var_dump(false instanceof stdClass);
90 Fatal error: instanceof expects an object instance, constant given
91 */

<?php
$c = ‘MyClass2‘;
$e = ‘MyClass2‘;
var_dump($c instanceof $e);
//boolean false 
???Fatal error