该语法仅在PHP 5.3和更高版本中受支持.以前的版本不了解该语法，因此会出现解析错误(T_PAAMAYIM_NEKUDOTAYIM指的是::运算符).

That syntax is only supported in PHP 5.3 and later. Previous versions don't understand that syntax, hence your parse error (T_PAAMAYIM_NEKUDOTAYIM refers to the :: operator).

在以前的版本中，您可以尝试call_user_func()，将包含类名及其方法名的数组传递给它:

In previous versions you can try call_user_func(), passing it an array containing the class name and its method name:

$variable_class_name = 'foo';
call_user_func(array($variable_class_name, 'bar'));