Section 12th-Automatic loading of classes-Classes and Objects in PHP5 [12]

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Section 12th-Automatic loading of classes

When you try to use an undefined class, PHP reports a fatal error. The workaround is to add a class that can include a file with include. After all, you know which class to use. However, PHP provides automatic loading of classes, which can save programming time. When you try to use a class that PHP does not organize into, it looks for a __autoload global function. If this function is present, PHP calls 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 tries to produce an instance of class user, PHP executes __autoload. The script assumes that the User class is defined in class_user.php. PHP returns the lowercase of the name, regardless of whether the call is uppercase or lowercase.

Listing 6.15 Class autoloading
<?php
Define AutoLoad function
function __autoload ($class)
{
Include ("Class_". Ucfirst ($class). ". php");
}

Use a class which must be autoloaded
$u = new User;
$u->name = "Leon";
$u->printname ();
?>