Online PHP editor | output for vMc1N

<?php // Reduced core class from MediaWiki to demonstrate an issue starting with 7.1.0alpha2 // https://github.com/wikimedia/mediawiki/blob/master/includes/Hooks.php class Hooks { protected static $handlers = array(); public static function register( $name, $callback ) { if ( !isset( self::$handlers[$name] ) ) { self::$handlers[$name] = array(); } self::$handlers[$name][] = $callback; } public static function run( $event, array $args = array() ) { foreach ( self::$handlers[$event] as $hook ) { if ( !is_array( $hook ) ) { $hook = array( $hook ); } if ( !array_filter( $hook ) ) { continue; } elseif ( is_array( $hook[0] ) ) { $hook = array_merge( $hook[0], array_slice( $hook, 1 ) ); } if ( $hook[0] instanceof Closure ) { $func = "hook-$event-closure"; $callback = array_shift( $hook ); } elseif ( is_object( $hook[0] ) ) { $object = array_shift( $hook ); $method = array_shift( $hook ); if ( $method === null ) { $method = "on$event"; } $func = get_class( $object ) . '::' . $method; $callback = array( $object, $method ); } elseif ( is_string( $hook[0] ) ) { $func = $callback = array_shift( $hook ); } $retval = null; $badhookmsg = null; $hook_args = array_merge( $hook, $args ); $retval = call_user_func_array( $callback, $args ); } } } Hooks::register( 'foo', function( &$foo, &$var ) { $var = $var . '-bar'; } ); //Stub class using &$this as direct reference class Foo { public function doSomething( $var ) { Hooks::run( 'foo', array( &$this, &$var ) ); return $var; } } // Stub class causes no error after $this is being redeclared class Foo2 { public function doSomething( $var ) { $foo = $this; Hooks::run( 'foo', array( &$foo, &$var ) ); return $var; } } // Causes an error $fooA = new Foo(); $varA = $fooA->doSomething( '123' ); echo "Foo: \n"; echo $varA . "\n"; // Causes no error $fooB = new Foo2(); $varB = $fooB->doSomething( '123' ); echo "Foo2: \n"; echo $varB;