OOP PHP

property-overloading.php

<?php  
 class PropertyTest  
 {  
    /** Location for overloaded data. */
    private $data = array();

    /** Overloading not used on declared properties. */  
    public $declared = 1;  

    /** Overloading only used on this when accessed outside the class. */  
    private $hidden = 2;  

    public function __set($name, $value)  
    {  
        echo "Setting '$name' to '$value'\n";  
        $this->data[$name] = $value;  
    }  

    public function __get($name)  
    {  
        echo "Getting '$name'\n";  
        
        if (array_key_exists($name, $this->data)) {  
            return $this->data[$name];  
        }
 
        $trace = debug_backtrace();  
        trigger_error(  
            'Undefined property via __get(): ' . $name .  
            ' in ' . $trace[0]['file'] .  
            ' on line ' . $trace[0]['line'],  
            E_USER_NOTICE
        );  
        
        return null;  
    }  

    public function __isset($name)  
    {  
        echo "Is '$name' set?\n";  
        return isset($this->data[$name]);  
    }  

    public function __unset($name)  
    {  
        echo "Unsetting '$name'\n";  
        unset($this->data[$name]);  
    }  

    public function getHidden()  
    {  
        return $this->hidden;  
    }  
}  

echo "<pre><br/>";  

$obj = new PropertyTest;  
$obj->a = 1;  

echo $obj->a . "<br/><br/>";  
var_dump(isset($obj->a));  
unset($obj->a);  
var_dump(isset($obj->a));  
echo "<br/>";  

echo $obj->declared . "<br/><br/>";  

echo "Let's experiment with the private property named 'hidden':<br/>";  
echo "Privates are visible inside the class, so __get() not used...<br/>";  
echo $obj->getHidden() . "<br/>";  
echo "Privates not visible outside of class, so __get() is used...<br/>";  
echo $obj->hidden . "<br/>";  
?>