General method for catching and handling exceptions thrown to child classes

Question

Assuming I have a parent class:

class Parent { //... } 

and a child class with methods:

 class Child extends Parent { public function foo() { // process and return data } public function bar() { // process and return data } // way more methods... } 

that is, is there a general way in PHP to handle any exceptions thrown by child methods? For example, a Parent class handler? Or do I need to wrap all the method bodies in a separate try-catch block?

What I want to achieve is to return an empty array() if any of the child methods throws any exception.

Answer 1

Yes it is possible. Well, the parent cannot know all the possible child methods, but he can know when the undefined method is called, implementing the __call magic method.

We can use this method to dynamically create a try-catch wrapper.

Add this method to your parent:

 public function __call($method, $args) { // If method call ends with 'Safe' $isSafeMethod = substr($method, -strlen('Safe')) === 'Safe'; if (!$isSafeMethod) { trigger_error('Call to undefined method '.__CLASS__.'::'.$method.'()', E_USER_ERROR); return null; } // Strip 'Safe' suffix from method name $wrappedMethodName = substr($method, 0, strpos($method, 'Safe')); try { return $this->$wrappedMethodName($args); } catch (Exception $e) { return []; } } 

Now, anytime you want to call this try-catch wrapper, just add "Safe" to the name of the method you want to wrap. Full code + example:

 class TestParent { public function __call($method, $args) { // If method call ends with 'Safe' $isSafeMethod = substr($method, -strlen('Safe')) === 'Safe'; if (!$isSafeMethod) { trigger_error('Call to undefined method '.__CLASS__.'::'.$method.'()', E_USER_ERROR); return null; } // Strip 'Safe' suffix from method name $wrappedMethodName = substr($method, 0, strpos($method, 'Safe')); try { return $this->$wrappedMethodName($args); } catch (Exception $e) { return []; } } } class TestChild extends TestParent { public function throwingMethod() { throw new RuntimeException(); } public function succeedingMethod() { return 'Success'; } } $child = new TestChild(); // With 'Safe' try-catch invoked in parent var_dump($child->throwingMethodSafe()); // Empty array var_dump($child->succeedingMethodSafe()); // 'Success' // Without 'Safe' try-catch var_dump($child->throwingMethod()); // throws RuntimeException as expected 

Output to 3v4l.org

Sidenote: Please do not catch the Exception class, because it is too general and will debug the living hell later ("Why does this method return an array?")

Answer 2

From my personal experience, create a custom exception handler and return an empty array if you get this exception. This link will help you understand exception handling in PHP: https://www.w3schools.com/php/php_exception.asp http://php.net/manual/en/language.exceptions.php