php ajax 实现三级省市区联动

public function getdiqudaima(){
		
			$rs = $this->db->table('diqudaima')
					   ->field("province,city,zonename,zonecode")
					   ->where("areaid=1 ")
					   ->getAll();
			$this->db->lastSql();
			return $rs;
		}
		public function getq($code,$n){
		$where = "and zonecode like '$code%'";
			$rs = $this->db->table('diqudaima')
					   ->field("province,city,zonename,zonecode")
					   ->where("areaid = $n ".$where)
					   ->getAll();
			return $rs;
		}

public function showdiqu(){
			$test = load_model('Test');
			$data = $test->getdiqudaima();
			$this->output->set('data',$data);
			$this->output->display('test.html');
			
		}
		public function showcity(){
			$test = load_model('Test');
			$code = $this->input->getTrim('code');
			$datacity = $test->getq($code,2);
			echo json_encode($datacity);
		}
		public function showqu(){
			$test = load_model('Test');
			$code = $this->input->getTrim('code');
			$datacity = $test->getq($code,3);
			echo json_encode($datacity);
		}

请选择市"); 		
				for(var p in obj){
					$("#city").append(""+obj[p].zonename+"");
				    
				}
			}
		);	
	}
	function getq(){
		var a = $("#pro").val();
		$.post("?c=Test&a=showqu",{code: a},
			function(data){
				var obj = eval('('+data+')');
				$("#zone").empty();
				$("#zone").prepend("请选择区"); 		
				for(var p in obj){
					$("#zone").append(""+obj[p].zonename+"");
				    
				}
			}
		);
	}
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