Why doesn't PHP catch a "Class not found" error? - php

Question

In the following example, if the class does not exist, I want to catch the error and create a Null class instead.
But in spite of my try/catch statements, PHP simply tells me Class 'SmartFormasdfasdf' not found.
How can I get PHP to catch the 'class not found' error?
<?php
class SmartFormLogin extends SmartForm {
public function render() {
echo '<p>this is the login form</p>';
}
}
class SmartFormCodeWrapper extends SmartForm {
public function render() {
echo '<p>this is the code wrapper form</p>';
}
}
class SmartFormNull extends SmartForm {
public function render() {
echo '<p>the form "' . htmlentities($this->idCode) . '" does not exist</p>';
}
}
class SmartForm {
protected $idCode;
public function __construct($idCode) {
$this->idCode = $idCode;
}
public static function create($smartFormIdCode) {
$className = 'SmartForm' . $smartFormIdCode;
try {
return new $className($smartFormIdCode);
} catch (Exception $ex) {
return new SmartFormNull($smartformIdCode);
}
}
}
$formLogin = SmartForm::create('Login');
$formLogin->render();
$formLogin = SmartForm::create('CodeWrapper');
$formLogin->render();
$formLogin = SmartForm::create('asdfasdf');
$formLogin->render();
?>
Solution:
Thanks #Mchl, this is how I solved it then:
public static function create($smartFormIdCode) {
$className = 'SmartForm' . $smartFormIdCode;
if(class_exists($className)) {
return new $className($smartFormIdCode);
} else {
return new SmartFormNull($smartFormIdCode);
}
}

Answer 1

Because it's a fatal error. Use class_exists() function to check if class exist.
Also: PHP is not Java - unless you redefined default error handler, it will raise errors and not throw exceptions.

Answer 2

Old question, but in PHP7 this is a catchable exception. Though I still think the class_exists($class) is a more explicit way to do it. However, you could do a try/catch block using the new \Throwable exception type:
$className = 'SmartForm' . $smartFormIdCode;
try {
return new $className($smartFormIdCode);
} catch (\Throwable $ex) {
return new SmartFormNull($smartformIdCode);
}

Answer 3

php >= 7.0
php can catch 'class not found' as Throwable
try {
return new $className($smartFormIdCode);
} catch (\Throwable $ex) {
return new SmartFormNull($smartformIdCode);
}

Answer 4

You need to use class_exists to see if the class exists before you try and instantiate it.
Incidentally, if you're using a class autoloader, be sure to set the second arg to true.

Answer 5

Because php emits fatal error when you ty to create new object of non existing class. To make it work you will need php >= 5.3 and autoload function, where you should try to look for file with class definition or throw your custom exception.