What is autoloading classes in PHP ?
Last Updated :
14 Oct, 2022
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 $class_name . '.php';
});
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Note: The class will be loaded from its corresponding “.php” file when it comes into use for the first time.
Autoloading:
Example 1: This example shows how a class is registered for autoloading.
PHP
<?php
spl_autoload_register(function ($class_name) {
include $class_name . '.php';
});
$obj = new test1();
$obj2 = new test2();
echo "objects of test1 and test2 class created successfully";
?>
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Output:
objects of test1 and test2 class created successfully
Note: If the corresponding “.php” file having class definition is not found, the following error will be displayed.
Output:
Warning: include(test1.php): failed to open stream:
No such file or directory in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 3
Warning: include(): Failed opening ‘test1.php’ for inclusion (include_path=’.:/usr/local/lib/php’)
in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 3
Fatal error: Uncaught Error: Class ‘test1’ not found in
/home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php:5
Stack trace:
#0 {main}
thrown in /home/guest/sandbox/5efa1ebc-c366-4134-8ca9-9028c8308c9b.php on line 5
Autoloading with exception handling
Example 2:
PHP
<?php
spl_autoload_register(function($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";
}
?>
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Output:
Unable to load test1.
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