Section 12 Automatic loading of classes [12]_PHP Tutorial

PHP will report a fatal error when you try to use an undefined class. The solution is to add a class, which can be included in a file. After all, you know which class to use. However, PHP provides automatic loading of classes. function, which can save programming time. When you try to use a class that PHP has not organized into, it will look for a global function __autoload. If this function exists, PHP will call it with a parameter, which is the name of the class. .

Example 6.15 illustrates how __autoload is used. It assumes that each file in the current directory corresponds to a class. When the script attempts to generate an instance of class User, PHP will execute __autoload. The script assumes class_User There is a User class defined in .php. Regardless of whether the call is in uppercase or lowercase, PHP will return the lowercase name.

Listing 6.15 Class autoloading
//define autoload function
function __autoload($class)
{
include("class_" . ucfirst($class) . ".php");
}

//use a class that must be autoloaded
$u = new User;
$u->name = "Leon";
$u->printName();
?>