Legacy default SPL loader that tries class filenames with registered extensions.
What It Does
spl_autoload_register() allows a predictable custom class loader Prefer an explicit class map or Composer PSR-4 autoloading; filename resolution depends on include_path and extensions.
Requirements and Compatibility
Available in the PHP runtime; use PHP 8 or later for the shown typed, modern examples.
Syntax, Inputs and Results
The arguments shown below are concrete values for this function; their types and ranges matter. The example checks return data rather than assuming that every operation succeeds.
Example 1: Basic Use
Demonstrates the primary behavior.
<?php
spl_autoload_extensions('.php');
// With a matching class file on the configured include_path:
spl_autoload('Report');Example 2: Another Case
Handles an alternative input or use case.
<?php
$previous = spl_autoload_extensions();
spl_autoload_extensions('.class.php,.php');
if (is_file(__DIR__ . '/Report.class.php')) {
set_include_path(__DIR__ . PATH_SEPARATOR . get_include_path());
spl_autoload('Report');
}
echo spl_autoload_extensions(), "\n";
spl_autoload_extensions($previous);Practical Example
Puts the function into a larger practical task.
<?php
// For modern code, prefer a predictable class-to-path loader:
spl_autoload_register(static function (string $class): void {
$file = __DIR__ . '/src/' . str_replace('\\', '/', $class) . '.php';
if (is_file($file)) require $file;
});For production, apply the compatibility and edge-case limits described below.
Important Behavior and Edge Cases
Prefer an explicit class map or Composer PSR-4 autoloading; filename resolution depends on include_path and extensions.
Comparison with Related Functions and Tools
| Subject | Key difference |
|---|---|
| spl_autoload() | spl_autoload_register() allows a predictable custom class loader |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Calling spl_autoload() without its required input or supported extension | Check the extension, supply valid arguments, and handle false or exceptions according to the function. |
| Assuming spl_autoload() guarantees a valid or safe image | Inspect the return and avoid exposing debug output to website visitors. |
| Confusing the operation with a related API | spl_autoload_register() allows a predictable custom class loader |
Key Takeaways
- Legacy default SPL loader that tries class filenames with registered extensions.
- Prefer an explicit class map or Composer PSR-4 autoloading; filename resolution depends on include_path and extensions.
- Choose the companion API described in the comparison table when the job differs.
Use these examples as a starting point, then validate the result with the actual PHP build, dependencies and inputs used by your application.