How to load classes in PHP ?

0 0 1 minute read

PHP load classes are used for declaring its object etc. in object oriented applications. PHP parser loads it automatically, if it is registered with spl_autoload_register() function. PHP parser gets the least chance to load class/interface before emitting an error.

Syntax:

spl_autoload_register(function ($class_name) {
  include $class_name . '.php';
});

The class will be loaded from its corresponding “.php” file when it comes into use for the first time.

Autoloading

Example:

PHP

<?php 
    spl_autoload_register(function ($class_name) { 
        include $class_name . '.php'; 
    }); 
    $obj = new mytest1(); 
    $obj2 = new mytest2(); 
    echo "Objects of mytest1 and mytest2 "
        + "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.

Warning: include(): Failed opening 'test10.php' for 
inclusion (include_path='C:\xampp\php\PEAR') in line 4
PHP Fatal error: Uncaught Error: Class 'test10' not found.

Autoloading with exception handling

Example:

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"; 
    } 
?>