class_exists throws on missing extends/implements and fatal on missing trait

Affected page

https://www.php.net/manual/en/function.class-exists.php

Issue description

class_exists will throw if a class is autoloaded (= 2nd arg is true = default!), but any extends/implements of that class do not exist and cannot be autoloaded

Steps to reproduce

spl_autoload_register( function ( $class_name ) { 
    if ( $class_name === 'Foo' ) {
        require __DIR__ . '/foo.php';
    }
} );
class_exists( Foo::class );

foo.php

class Foo extends Bar {}

Suggested fix

Mention that it can throw an exception if the any of the classes that class extends/implements fails

Mention that it will result in a fatal E_ERROR if any of the "trait use" of the class do not exist (https://github.com/php/php-src/issues/21106)

Read the class_exists documentation at the affected PHP manual page and compare its current autoloading behavior description with the reproduction examples. Update the documentation to mention exceptions from missing parent classes or interfaces and fatal errors from missing traits, using the linked PHP issue for the trait behavior. Done means both failure modes are accurately documented.