How can I catch a "catchable fatal error" on PHP type hinting?

Question

I am trying to implement Type Hinting of PHP5 on one of my class,

class ClassA {     public function method_a (ClassB $b)     {} }  class ClassB {} class ClassWrong{} 

Correct usage:

$a = new ClassA; $a->method_a(new ClassB); 

producing error:

$a = new ClassA; $a->method_a(new ClassWrong); 

Catchable fatal error: Argument 1 passed to ClassA::method_a() must be an instance of ClassB, instance of ClassWrong given...

Is it possible to catch that error(since it says "catchable")? and if yes, how?

Answer 1

Update: This is not a catchable fatal error anymore in php 7. Instead an "exception" is thrown. An "exception" (in scare quotes) that is not derived from Exception but Error; it's still a Throwable and can be handled with a normal try-catch block. see https://wiki.php.net/rfc/throwable-interface

E.g.

<?php class ClassA {   public function method_a (ClassB $b) { echo 'method_a: ', get_class($b), PHP_EOL; } } class ClassWrong{} class ClassB{} class ClassC extends ClassB {}   foreach( array('ClassA', 'ClassWrong', 'ClassB', 'ClassC') as $cn ) {     try{       $a = new ClassA;       $a->method_a(new $cn);     }     catch(Error $err) {       echo "catched: ", $err->getMessage(), PHP_EOL;     } } echo 'done.'; 

prints

catched: Argument 1 passed to ClassA::method_a() must be an instance of ClassB, instance of ClassA given, called in [...] catched: Argument 1 passed to ClassA::method_a() must be an instance of ClassB, instance of ClassWrong given, called in [...] method_a: ClassB method_a: ClassC done. 

---

Old answer for pre-php7 versions:
http://docs.php.net/errorfunc.constants says:

E_RECOVERABLE_ERROR ( integer )
Catchable fatal error. It indicates that a probably dangerous error occured, but did not leave the Engine in an unstable state. If the error is not caught by a user defined handle (see also set_error_handler()), the application aborts as it was an E_ERROR.

see also: http://derickrethans.nl/erecoverableerror.html

e.g.

function myErrorHandler($errno, $errstr, $errfile, $errline) {   if ( E_RECOVERABLE_ERROR===$errno ) {     echo "'catched' catchable fatal error\n";     return true;   }   return false; } set_error_handler('myErrorHandler');  class ClassA {   public function method_a (ClassB $b) {} }  class ClassWrong{}  $a = new ClassA; $a->method_a(new ClassWrong); echo 'done.'; 

prints

'catched' catchable fatal error done. 

edit: But you can "make" it an exception you can handle with a try-catch block

function myErrorHandler($errno, $errstr, $errfile, $errline) {   if ( E_RECOVERABLE_ERROR===$errno ) {     echo "'catched' catchable fatal error\n";     throw new ErrorException($errstr, $errno, 0, $errfile, $errline);     // return true;   }   return false; } set_error_handler('myErrorHandler');  class ClassA {   public function method_a (ClassB $b) {} }  class ClassWrong{}  try{   $a = new ClassA;   $a->method_a(new ClassWrong); } catch(Exception $ex) {   echo "catched\n"; } echo 'done.'; 

see: http://docs.php.net/ErrorException