07c08-2.php

介绍PHP5的给类型函数应用

<?php
// Define a class that overloads a variable name by allowing the same
//  name to hold a number, and text.
class Multi_Data_Holder {
    // variables to hold various versions of the same named property
    private $number = array();
    private $text = array();
    
    // Define __set, which stores data based upon the type of value.
    public function __set($name, $value) {
        // Check if it is one of the types we are allowing, and store
        //  appropriately. If it is an int or float, store it as a number:
        if (is_int($value) || is_float($value)) {
            $this->number[$name] = $value;
        } elseif (is_string($value)) {
            $this->text[$name] = $value;
        }
    }
    
    // Defining isset to understand the 'multi' nature of values here.
    public function __isset($name) {
        // If it exists in either case, claim it exists.
        return isset($this->number[$name]) || isset($this->text[$name]);
    }
    
    // Define a method such that unset will unset all values.
    public function __unset($name) {
        unset($this->number[$name]);
        unset($this->text[$name]);        
    }

    // It won't be possible to define a get that knows which one to return,
    //  so let's define a function instead that takes a second parameter of
    //  either 'number' or 'text' to determine which one to read:
    public function value($name, $type) {
        // Use the $type as a variable variable to return the right value:
        return $this->{$type}[$name];
    }
}

// Create a data holding object
$data = new Multi_Data_Holder();

// Store a number, and the English representation of the number
$data->x = 173;
$data->x = 'One Hundred Seventy Three';

// Now echo the number and it's text:
echo '<p>The number ', $data->value('x', 'number'), ' is written: ',
    $data->value('x', 'text'), '</p>';

// Now unset the value, and then use isset to ensure that it happened.
unset($data->x);
echo '<p>The value is ', isset($data->x) ? '' : 'not ', 'set.</p>';
?>