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Overload in php

Can anyone say what the data below the given lines means?

The following lines are copied from the PHP manual :

Note:

It is not possible to use overloaded properties in a different construction language than isset (). This means that if empty () is called on an overloaded property, the overloaded method is not called.

To get around this limitation, the overloaded property must be copied to a local variable in the scope, and then passed to empty ().

BUT it’s not that we cannot call empty () with overloaded properties, when I called empty (), it called __isset ()

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3 answers

This is a documentation error:

<?php
class PropNameReturn {
    function __isset($propname){
          return true;

    }
    function __get($propname){
          echo 'Yes, it IS called!'.PHP_EOL;
          return $propname;
    }
}
$o = new PropNameReturn();
var_dump(empty($o->this_prop_name));
//Yes, it IS called!
//bool(false)
$b = new stdClass();
var_dump(empty($b->this_prop_name));
//bool(true)
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, . PHP 5.2

, , __get() empty(), __isset().

empty() true, __isset() true, __get() .

:

class Foo {
    function __get($name) {
        if ($name == "bar")
            return '';
    }
    function __isset($name) {
        if ($name == "bar")
            return true;
    }
}
$foo = new Foo();
echo $foo->bar . PHP_EOL;  // outputs "" - correct
echo var_export(isset($foo->bar)) . PHP_EOL; // outputs "true" - correct

$bar = $foo->bar;

// outputs both "true" -- so the manual is wrong here
echo var_export(empty($foo->bar)) . PHP_EOL;
echo var_export(empty($bar)) . PHP_EOL;

.

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-, , , :

PHP - . :

class MyClass {
  public $foo = 'bar';
}

$Instance = new MyClass();
echo $Instance->foo;

, "", . :

class MyOverloadedClass {
  public function __get($variable) {
    return $variable == 'foo' ? 'bar' : '';
  }
}

 $Instance = new MyOverloadedClass();
 echo $Instance->foo;

, MyOverloadedClass:: $foo , __ge , ( "foo" ). __get , foo "bar"

PHP. , , , . : exit, die, print, echo, isset empty.

isset() - . __isset, , , - isset . empty() true , , E_NOTICE. :

: empty() , __get(), IF ONLY, __isset(), true :

empty () will not call your overloaded __get () method. It will look in the class definition to find out if this parameter exists. If so, it will evaluate whether it is empty or not. However, accessing the parameters of the undefined class causes an error. In my first example, I would throw an error by querying the string $ Instance-> bar, because it does not exist. This is the same error you would get if you asked

empty( $Instance->foo );

In the second example. Hope this helps.

For more information on how to apply this to functions or setting variables, see the page you mentioned.

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