1..24
# ->clear()
 -  clears all parameters
 -  clears all parameters
# ->get()
 -  returns the parameter value for the given key
 -  returns null if the key does not exist
 -  returns a reference for the given key
 -  takes the default value as its second argument
# ->getNames()
 -  returns all key names
# ->getAll()
 -  returns all parameters
# ->has()
 -  returns true if the key exists
 -  returns false if the key does not exist
 -  returns true if the key exist, even if the value is null
# ->remove()
 -  removes the key from parameters
 -  removes the key from parameters
 -  takes a default value as its second argument
 -  removes the key from parameters
# ->set()
 -  sets the value for a key
 -  sets the value for a key, not a reference
# ->setByRef()
 -  sets the value for a key
 -  sets the value for a key as a reference
# ->add()
 -  adds an array of parameters
 -  adds an array of parameters, not a reference
# ->addByRef()
 -  adds an array of parameters
 -  adds a reference of an array of parameters
# ->serialize() ->unserialize()
 - sfParameterHolder implements the Serializable interface
# Looks like everything went fine.