In order to use a class defined in another PHP script, we can incorporate it with include or require statements. However, PHP’s autoloading feature does not need such explicit inclusion. Instead, when a class is used (for declaring its object etc.) PHP parser loads it automatically, if it is registered with spl_autoload_register() function. Any number of classes can thus be registered. This way PHP parser gets a last chance to load the class/interface before emitting an error.
Syntax:
PHP
spl_autoload_register(function ($class_name) { include $class_name . '.php'; }); |
Note: The class will be loaded from its corresponding “.php” file when it comes into use for the first time.
Autoloading:
Example 1: This example shows how a class is registered for autoloading.
PHP
<?php spl_autoload_register(function ($class_name) { include $class_name . '.php'; }); $obj = new test1(); $obj2 = new test2(); echo "objects of test1 and test2 class created successfully"; ?> |
Output:
objects of test1 and test2 class created successfully
Note: If the corresponding “.php” file having class definition is not found, the following error will be displayed.
Output:
Warning: include(test1.php): failed to open stream:
No such file or directory in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 3
Warning: include(): Failed opening ‘test1.php’ for inclusion (include_path=’.:/usr/local/lib/php’)
in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 3
Fatal error: Uncaught Error: Class ‘test1’ not found in
/home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php:5
Stack trace:
#0 {main}
thrown in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 5
Autoloading with exception handling
Example 2:
PHP
<?php spl_autoload_register(function($className) { $file = $className . '.php'; if (file_exists($file)) { echo "$file included\n"; include $file; } else { throw new Exception("Unable to load $className."); } }); try { $obj1 = new test1(); $obj2 = new test10(); } catch (Exception $e) { echo $e->getMessage(), "\n"; } ?> |
Output:
Unable to load test1.
