HTTP POST - Undefined index Error

[learn-php]

Hello there,

 

I am coding Arduino micro controller, and intended to GET the data from server MySQL db through php to turn ON/OFF LED.

I could able to GET the data from manually updated MySQL db value, even I could able to successfully change the data of MySQL db from micro controller POST method.

But I am getting error when trying to change the MySQL db value from browser using online POST tool,

Following is PHP code at server

8  $api_key_value ="XXXXXXXXX";//Sample
9  $api_key ="";
10 $status = "";
11 $id ="";
12 
13 if ($_SERVER["REQUEST_METHOD"] == "POST") {
14    $api_key = test_input($_POST["api_key"]);
15    if($api_key == $api_key_value) {
        $id     = test_input($_POST["id"]);
        $status = test_input($_POST["status"]);

        // Create connection
        $conn = new mysqli($servername, $username, $password, $dbname);
        // Check connection
        if ($conn->connect_error) {
            die("Connection failed: " . $conn->connect_error);
        } 

        //$sql = "INSERT INTO led (status)
        //VALUES ('" . $status . "')";
        $sql = "UPDATE led SET status='$status' WHERE id='$id'";

        if ($conn->query($sql) === TRUE) {
            echo "New record created successfully";
        } 
        else {
            echo "Error: " . $sql . "<br>" . $conn->error;
        }
    
        $conn->close();
    }
    else {
        echo "Wrong API Key provided.";
    }

}
else {
    echo "No data posted with HTTP POST.";
}

function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}

Post Command:

http://url/MySQL_POST.php?api_key=XXXXXXXXX&id=1&status=on

Response/Error:

Notice: Undefined index:  api_key in <PATH>/MySQL_POST.php on line 14
Wrong API Key provided.

Could be a basic issue, but I am very new to php coding and cannot solve this problem yet.

Could someone please help?

Thanks.

[gw1500se]

I don't see how you are getting to line 14 at all. You are checking for POST but the URL is GET. Perhaps you should be using this:

if (isset($api_key)) {

 

[learn-php]

Hi, Thanks for your response.

I tried changing code as you mentioned also tried to echo input arguments.

It still enters condition, but did not update MySQL db as values were null.

Modified code,

8  $api_key_value ="XXXXXXXXX";
9  $api_key ="";
10 $status = "";
11 $id ="";
12 
13 if ($_SERVER["REQUEST_METHOD"] == "POST") {
14    echo "value of api_key=" . $api_key . "\n";
15    echo "value of id=" . $id . "\n";
16    echo "value of status=" . $status . "\n";
17    if (isset($api_key) and isset($id) and isset($status)) {
18        $api_key = test_input($_POST["api_key"]);
19        $id     = test_input($_POST["id"]);
20        $status = test_input($_POST["status"]);

        // Create connection
        $conn = new mysqli($servername, $username, $password, $dbname);
        // Check connection
        if ($conn->connect_error) {
            die("Connection failed: " . $conn->connect_error);
        } 

        //$sql = "INSERT INTO led (status)
        //VALUES ('" . $status . "')";
        $sql = "UPDATE led SET status='$status' WHERE id='$id'";

        if ($conn->query($sql) === TRUE) {
            echo "New record created successfully";
        } 
        else {
            echo "Error: " . $sql . "<br>" . $conn->error;
        }
    
        $conn->close();
    }
//    else {
//        echo "Wrong API Key provided.";
//    }

}
else {
    echo "No data posted with HTTP POST.";
}

function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}

 

Response:

value of api_key= value of id= value of status= Notice: Undefined index: api_key in <url>/post_test.php on line 18 Notice: Undefined index: id in <url>/post_test.php on line 19 Notice:Undefined index: status in <url>/post_test.php on line 20 New record created successfully

 

Kindly suggest any other preferred method to achieve if this is incorrect. 

Edited February 15, 2021 by learn-php

[gw1500se]

Monday morning. 🙁 I told you completely wrong since $_POST will always have a value, so you need to use 'empty' instead. Also I meant for it to replace your first 'if'.

 if (!empty($_POST["api_key")) {

That being said you still have the same problem. Since the URL is using GET you need to use the $_GET array, not $_POST.