php[world] 2015 Schedule Announced

INSTANCEOF

PHP code

<?php
/*
 * 
 * opcode number: 138
 */
$obj = new A();

if (
$obj instanceof A) {
   echo 
'A';
}
?>

PHP opcodes

Function name: (null)

Compiled variables: !0=$obj

line#op fetchextreturn operands
60 ZEND_FETCH_CLASS   :0 'A'
 1 NEW   $1 :0
 2 DO_FCALL_BY_NAME  0   
 3 ASSIGN     !0,$1
84 ZEND_FETCH_CLASS   :4 'A'
 5 ZEND_INSTANCEOF   ~5 !0,$4
 6 JMPZ     ~5,->9
97 ECHO     'A'
108 JMP     ->9
119 RETURN     1
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User Contributed Notes 5 notes

up
17
cody at codysnider dot com
3 years ago
When checking instanceof against a subclass of the class in question, it will return true.

<?php

class Foo {

    public
$foobar = 'Foo';
   
    public function
test() {
        echo
$this->foobar . "\n";
    }

}

class
Bar extends Foo {

    public
$foobar = 'Bar';

}

$a = new Foo();
$b = new Bar();

echo
"use of test() method\n";
$a->test();
$b->test();

echo
"instanceof Foo\n";
var_dump($a instanceof Foo); // TRUE
var_dump($b instanceof Foo); // TRUE

echo "instanceof Bar\n";
var_dump($a instanceof Bar); // FALSE
var_dump($b instanceof Bar); // TRUE

echo "subclass of Foo\n";
var_dump(is_subclass_of($a, 'Foo')); // FALSE
var_dump(is_subclass_of($b, 'Foo')); // TRUE

echo "subclass of Bar\n";
var_dump(is_subclass_of($a, 'Bar')); // FALSE
var_dump(is_subclass_of($b, 'Bar')); // FALSE

?>

Result (CLI, 5.4.4):

use of test() method
Foo
Bar
instanceof Foo
bool(true)
bool(true)
instanceof Bar
bool(false)
bool(true)
subclass of Foo
bool(false)
bool(true)
subclass of Bar
bool(false)
bool(false)
up
3
krall dot eugene at gmail dot com
3 months ago
When checking instanceof against a class that implements the class in question, it will return true.

<?php

interface ExampleInterface
{
    public function
interfaceMethod();

}

class
ExampleClass implements ExampleInterface
{
    public function
interfaceMethod()
    {
        return
'Hello World!';
    }
}

$exampleInstance = new ExampleClass();

if(
$exampleInstance instanceof ExampleInterface)
    echo
'Yes, it is';
else
    echo
'No, it is not';

?>

The result:

Yes, it is
up
9
asdf at asdf dot com
3 years ago
Please note, that you get no warnings on non-existent classes:

<?php
class A() {
}

$a = new A();

$exists = ($a instanceof A); //TRUE
$exists = ($a instanceof NonExistentClass); //FALSE
up
0
portugal {at} jawira {dot} com
13 days ago
I'm commenting here because the note from "admin at torntech" is incomplete. You can perfectly replace "is_a()" function with "instanceof" operator. However you must use a variable to store the class name, otherwise you will get a Parse error:

<?php
$object
= new \stdClass();
$class_name = '\stdClass';

var_dump($object instanceof $class_name);    // bool(true)
var_dump($object instanceof '\stdClass');    // Parse error: syntax error, unexpected ''\stdClass'' (T_CONSTANT_ENCAPSED_STRING)
?>

Please go to Type Operators page for more details about "instanceof": http://php.net/manual/en/language.operators.type.php
up
0
admin at torntech dot com
4 months ago
Despite this section being opcode examples, for php 5.3+ see also is_a()
*Note php 5.0 - 5.2 is_a() was depreciated in favor of instanceof but was undepreciated in 5.3+.

Allows for string comparison against the class name and functions in the same manner as cody mentions like so.
<?php
namespace Foo{
    class
Bar {}
    class
Baz extends Bar{}
}
namespace {
   
$baz = new Foo\Baz;

   
var_dump($baz instanceof Foo\Bar);
   
/* returns bool(true) */

   
var_dump(is_a($baz, 'Foo\\Bar'));
   
/* returns bool(true) */

   
var_dump($baz instanceof 'Foo\\Bar');
   
/* returns Runtime parse error */
}
?>
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