Why php api is returning null after code rewrited with bind_result?

Question

I'm using this PHP API for android app to get token to send notification base on server and user[Phone]. problem is i'm getting error in app and only this part of my api is getting errors. which error is

<br />
<b>Notice</b>:  Undefined variable: token in <b>/home/meskand1/public_html/pasargad-drinkshop/db_functions.php</b> on line <b>390</b><br />
null

I've commented line 390 and function code below.

Code was working fine with get_Result & fetch_assoc, but because online host didn't supported mysqlnd, i've forced to change this. can anyone explain where is mistake happen and why? in tutorial with get_Result instructor returned $token, now with my code this is getting errors.

Here's the code in function:

public function getToken($phone,$isServerToken){
   $stmt = $this->conn->prepare("SELECT phone, token, isServerToken FROM `token` WHERE phone=? AND isServerToken=?") or die ($this->conn->error);
   $stmt->bind_param("ss",$phone,$isServerToken);
   $result = $stmt->execute();
   $stmt->bind_result($a,$b,$c);
   while ($stmt->fetch()){
       $token[] = ['phone' => $a, 'token' => $b, 'isServerToken' => $c];
   }
   $stmt->close();
   return $token; // => This is line 390
}

Call

if(isset($_POST['phone']) && isset($_POST['isServerToken'])){
   $userPhone = $_POST['phone'];
   $isServerToken = $_POST['isServerToken'];

   $token = $db->getToken(urlencode($userPhone),$isServerToken);

   echo json_encode($token);

} else {
   $response = "Required parameter (phone , isServerToken) is missing!";
   echo json_encode($response);
}

Nigel Ren · Accepted Answer · 2018-08-12 16:45:33Z

1

If your SQL doesn't match any data, $token is undefined as it is only ever set in the loop. You should at least initialise it before the loop just in case...

$stmt->bind_result($a,$b,$c);
$token = array();    // Initialise
while ($stmt->fetch())
{
    $token[] = ['phone' => $a, 'token' => $b, 'isServerToken' => $c];
}
$stmt->close();
return $token;

answered Aug 12, 2018 at 16:45

Nigel Ren

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4 Comments

Mohammad Eskandari Over a year ago

omg, u don't belive man if i just tell u i find it before i saw this answer, but this answer gimme best Confirmation, i've looked for another example and changed it to another method, in this method i've initialized like u said, then i've saw your answer and i've found best place to put it. Thanks mate.

Mohammad Eskandari Over a year ago

@PaulSpiegel any e.g. ? can u answer it base on top code? i've learned so many base on all these ideas, i'll be grateful if u make another answer base on what u've suggested.

Paul Spiegel Over a year ago

@MohammadEskandari - I removed my comment with fetch_all() since the manual says: "Available only with mysqlnd". However - ->fetch_assoc() in a loop might work for you. I don't see any use for bind_result() in your case.

Mohammad Eskandari Over a year ago

@PaulSpiegel thanks for your response, right now i'm using sharing host, which hosting service said it's premium :D, but in months i'll go for vps so i can fix mysqlnd problem. anyway, u already gimme a clue about another thing and it's amazing, if u could answer that example base on top code i would be happy to test it on local which is working without any problem with mysqlnd. thanks again.

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