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

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.

<?phpclass 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: ClassBmethod_a: ClassCdone.

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 errordone.

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