added login

app/scripts/database_queries.php

@@ -1,5 +1,10 @@
 <?php
 
+function handle_pdo_exception($e) {
+    print "Error!: " . $e->getMessage() . "<br/>";
+    die();
+}
+
 function get_Station() {
     try {
         $dbh = new PDO('mysql:host=mysql;dbname=ksp', 'grisu', 'secret');
@@ -8,9 +13,53 @@ function get_Station() {
         }
         $dbh = null;
     } catch(PDOException $e) {
-        print "Error!: " . $e->getMessage() . "<br/>";
-        die();
+        handle_pdo_exception($e);
     }
 }
 
-?>
+function check_user_id($con, $user_id) {
+    try {
+        $stmt = $con->prepare('SELECT user_id FROM users WHERE user_id = :user_id limit 1');
+        $stmt->execute(['user_id' => $user_id]);
+
+        if($stmt) {
+            return true;
+        } else {
+            return false;
+        }
+    } catch(PDOException $e) {
+        handle_pdo_exception($e);
+    }
+}
+
+function get_user_data_name($con, $user_name) {
+    try {
+        $stmt = $con->prepare('SELECT * FROM users WHERE user_name = :user_name limit 1');
+        $stmt->execute(['user_name' => $user_name]);
+        $stmt->setFetchMode(PDO::FETCH_ASSOC);
+        return $stmt->fetch();
+    } catch(PDOException $e) {
+        handle_pdo_exception($e);
+    }
+}
+
+function get_user_data_id($con, $user_id) {
+    try {
+        $stmt = $con->prepare('SELECT * FROM users WHERE user_id = :user_id limit 1');
+        $stmt->execute(['user_id' => $user_id]);
+        $stmt->setFetchMode(PDO::FETCH_ASSOC);
+        return $stmt->fetch();
+    } catch(PDOException $e) {
+        handle_pdo_exception($e);
+    }
+}
+
+function add_user($con, $username, $user_id, $user_group, $password, $salt) {
+    try {
+        $stmt = $con->prepare("INSERT INTO users (user_id, password, user_name, salt, user_group) VALUES (?, ?, ?, ?, ?)");
+        $stmt->bind_param("sssss", $user_id, $password, $username, $salt, $user_group);
+        $stmt->execute();        
+    } catch(PDOExeption $e) {
+        handle_pdo_exception($e);
+    }   
+}