Opcode Descriptions and Examples
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PHP手册

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
Opcode Descriptions and Examples
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PHP手册
PHP手册 - N: INSTANCEOF

用户评论:

asdf at asdf dot com (04-Apr-2012 06:13)

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

Sasanapuri Satish (13-Jul-2011 09:46)

The operator instanceof can also be used to determine whether an object of a class is inheriting property from another class or not.

Example:

<?php

class test
{    var $var;
    function disp()
   {
       echo "Inside the class";
   }
}

$obj=new test;

var_dump($obj instanceof test); // Prints bool(true)

?>