jquery - AJAX and PHP communication : the safe way -

as discussed in 1 of previous topics, i'm trying send json , php script. currently, working well. i've organized php script gets parameter in url , based on (with of switch statement) call appropriate functions. however, i've noted looking @ source, 1 can copy link php script , manipulate data through it. that's i'm not comfortable with. alternatives?

sample of .html ajax call:

function getalldata(){  $.ajax({     type: "post",     url: "datadao.php?f=getall",     datatype: "json",     async: false,     success: function(data){          $.each(json.parse(data), function(index, value) {           alert(value['firstname'] );         });     },     error: function(err){       alert('error!' + json.stringify(err));     }  });  } 

sample of php code

switch($_get['f']) { case 'getall':     $result = getall();     break; case 'getone':     $id = $_get['id'];     $result = getone($id);     break; case 'addto':     $result = addtoarray(); default: } 

there aren't alternatives. public facing interface http server, not javascript. must implement whatever input sanity checking, data escaping, authentication , authorization need @ server level.