property_exists

说明

bool property_exists ( mixed class, string property )

This function checks if the given property exists in the specified class (and if it was declared as public).

注: As opposed with isset(), property_exists() returns TRUE even if the property has the value NULL.

参数

class: A string with the class name or an object of the class to test for
property: The name of the property

范例

例子 1. A property_exists() example
<?php class myClass { public $mine; private $xpto; } var_dump(property_exists('myClass', 'mine')); //true var_dump(property_exists(new myClass, 'mine')); //true var_dump(property_exists('myClass', 'xpto')); //false, isn't public ?>

add a note User Contributed Notes

jcaplan at bogus dot amazon dot com
09-Jun-2006 05:35


The documentation leaves out the important case of new properties you add to objects at run time.  In fact, property_exists will return true if you ask it about such properties.



<?

class Y {}

$y = new Y;



echo isset( $y->prop ) ? "yes\n" : "no\n"; // no;

echo property_exists( 'Y', 'prop' ) ? "yes\n" : "no\n"; // no

echo property_exists( $y, 'prop' ) ? "yes\n" : "no\n"; // no



$y->prop = null;



echo isset( $y->prop ) ? "yes\n" : "no\n"; // no;

echo property_exists( 'Y', 'prop' ) ? "yes\n" : "no\n"; // no

echo property_exists( $y, 'prop' ) ? "yes\n" : "no\n"; // yes

?>

Pete W
02-Jun-2006 02:52


In a similar vein to the previous note, To check in PHP4 if an object has a property, even if the property is null:



<?php



if(array_key_exists('propertyName',get_object_vars($myObj)))

{

  // ..the property has been defined

}  

?>

timshel
15-Nov-2005 08:20


I haven't tested this with the exact function semantics of 5.1, but this code should implement this function in php < 5.1:



<?php

if (!function_exists('property_exists')) {

  function property_exists($class, $property) {

    if (is_object($class))

      $class = get_class($class);



    return array_key_exists($property, get_class_vars($class));

  }

}

?>

add a note

property_exists

说明

参数

返回值

范例

参见