Catchable fatal error Argument 1 passed to ClassA method a must be an instance of ClassB instance of ClassWrong given

0 votes

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?

Oct 22, 2020 in PHP by kartik
• 37,500 points
156 views

1 answer to this question.

0 votes

Hello @kartik,

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. 

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.

Hope it helps!!

Thank You!!

answered Oct 22, 2020 by Niroj
• 82,740 points

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