__construst () The constructor must be double underlined. Most magic methods are like this

Print $obj to see if the data is correct

// 1. Check whether the class exists

var_dump( class_exists('Staff') );// 2. Check whether the attribute exists

var_dump( property_exists('Staff', 'name') );// 3. Get all properties of 1 in the class

var_dump( get_class_vars('Staff') );// 4 . Get all attributes in the object

$a = new Staff;

var_dump( get_object_vars($a) );// 5. Get all methods in the class

var_dump( get_class_methods('Staff') );// 6. Get the class name of the object

var_dump( get_class($a) );