json - php web service method post -

hi have php web return json data usin json!encode when change post return null

<?php header('content-type: application/json; charset=utf-8');  include('settings.php'); mysql_connect($host,$user,$password); mysql_select_db($base);   mysql_query('set character set utf8'); $login = $_get['login']; $password = $_get['password'];   $req = "select * user username = '".$login."' , password = '".$password."'"; $sql=mysql_query($req); $nn=mysql_num_rows($sql);  $items = array("items" => null);  while ($data=mysql_fetch_array($sql)) {     $items["items"][] = array(         "id" => $data['id'],         "username" => $data['username'],         "password" => $data['password'],         "nom_prenom" => $data['nom_prenom'],         "nom_prenom_arabe" => $data['nom_prenom_arabe'],         "specialite" => $data['specialite'],         "specialite_arabe" => $data['specialite_arabe'],         "adresse" => $data['adresse'],         "adresse_arabe" => $data['adresse_arabe'],         "telephone_cabinet" => $data['telephone_cabinet'],         "gsm" => $data['gsm'],       ); }    echo json_encode($items,json_unescaped_unicode); ?> 

it returns

{"items":[{"id":"2","username":"**","password":"*","nom_prenom":"****","nom_prenom_arabe":"مهذب عبد الصمد ","specialite":"pediatrie","specialite_arabe":"إختصاصي في الامراض النفسية و العصبية","adresse":"av tahar sfar imm .el baraka sousse 4000","adresse_arabe":" 4000 شارع طاهر سفر عمارة البركة سوسة","telephone_cabinet":"73698521","gsm":"25631478"}]}

but

 $login = $_post['login'];  $password = $_post['password']; 

it return

 {"items":null} 

can explain me why :) thanks

because post invoke page has method , remplace post work expected.

another point it's discouraged use string concatenation when quering databases due security risk. use prepared statements instead.