explanation.md

Most of this is pretty simple, but we'll walk through the whole thing for the sake of completeness. Starting with the inner bit

return ${ ! ${''} = (new ReflectionClass( get_called_class() ) ) }->newInstanceArgs( func_get_args() );

return ${ ! ${''} = (new ReflectionClass( 'A' ) ) }->newInstanceArgs( func_get_args() );

return ${ ! ${''} = ReflectionClass('A') }->newInstanceArgs( func_get_args() );

The next bit is the magic, ${<identifier>} lets you access a variable with the name <identifier>, so with ${''} a variable with a name of '' is being accessed. Or in this case, the Reflection object is being assigned to the empty string variable. It is essentially equivilent to $GLOBALS[''] = ... .

return $GLOBALS[ ! $GLOBALS[''] = (ReflectionClass('A')) ]->newInstanceArgs( func_get_args() );

The empty string var is then negated with !, and since non-empty objects are truthy in PHP, it evaluates as false. Then the outer variable syntax converts the false value to a string to get a variable name, and false converts to an empty string, so the variable just created is accessed.

source.php

class A {
  public static function f()
  {
    return ${!${''}=(new ReflectionClass(get_called_class()))}->newInstanceArgs(func_get_args());
  }
}