PHP var_dump NULL error after SQL Query

Question

Hi there I have a website which query for the CarID after a user selects a BRAND from a webpage. Therefore a SELECT query would be executed and the CarID value would then be passed to a PHP variable. However currently the var_dump that I am using to debug the problem is giving a NULL value even though there is no error executing the SQL statement.

The database table:

The codes:

<?php // register.php
session_start();
include "dbconn.php";


$carcat = $_SESSION['selectedcarcat'];
$carbrand = $_POST['carbrand'];
$userid = $_SESSION['loginid'];
$username = $_SESSION['loginname'];
$startdate = $_POST['date1'];
$enddate = $_POST['date2'];
$pick = $_POST['pickuploc'];
$return = $_POST['returnloc'];
$calqty = 0;


    $selcaridsql = "SELECT carid FROM cars WHERE brand='$carbrand' ";
    
    echo $selcaridsql."<br>";

    $caridresult = $dbcnx->query($selcaridsql);

    echo "<br>".var_dump($caridresult);

    if ($caridresult->num_rows >0 )
      {
        echo '<br>Hello more than 1 <br>';  
      }

    else
    {
        echo '<br>Hello less than 1 <br>';
    }


    $caridrow = mysql_fetch_array($caridresult);

    echo var_dump($caridrow)."<br>"; 

    $carid = $caridrow['carid'];

    echo var_dump($carid)."<br>"; 
    
    if (!$caridresult) 
    {
        $errmessage = "Your carid select query failed.";
        echo "<script type='text/javascript'>alert('$errmessage');</script>";
    }


    echo '<br>Debug 1 ';
    echo '<br>The selected qty is '
        .$qtyresult1.'<br />';
    echo '<br>The calculated qty is '
        .$calqty.'<br />';
    echo '<br>The content carid is '
        .$carid.'<br />';
    echo '<br>The content userid is '
        .$userid.'<br />';
    echo '<br>The content start is '
        .$startdate.'<br />';
    echo '<br>The content end is '
        .$enddate.'<br />';
    echo '<br>The content pick is '
        .$pick.'<br />';
    echo '<br>The content return is '
        .$return.'<br />';
        echo '<br>The content carbrand is '
        .$carbrand.'<br />';
?>

The results that would be currently output:

SELECT carid FROM cars WHERE brand='Honda' 
object(mysqli_result)#2 (5) { ["current_field"]=> int(0) ["field_count"]=> int(1) ["lengths"]=> NULL ["num_rows"]=> int(1) ["type"]=> int(0) } 

Hello more than 1 
NULL 
NULL 

Debug 1 
The selected qty is 

The calculated qty is 0

The content carid is 

The content userid is 

The content start is 2016-10-28

The content end is 2016-10-29

The content pick is jurong

The content return is bishan

The content carbrand is Honda

It seems that the query is able to retrieve the data but I have no idea why the value would be a NULL. I have tried the SQL statement directly into the database and it works.

Thanks.

be sure that you have a proper value in var_dump($carbrand ) — ScaisEdge, Oct 27 '16 at 07:34
What is `$dbcnx` and why are you calling `mysql_fetch_array` instead of using the same database abstraction layer? — Ruslan Osmanov, Oct 27 '16 at 07:35
@scaisEdge Theres a proper value for carbrand. The SQL statement when echoed shows "Honda". — Specs, Oct 27 '16 at 07:48
@RuslanOsmanov $dbcnx is a database connection. @$dbcnx = new mysqli('localhost','values','values','values'); — Specs, Oct 27 '16 at 07:49

score 0 · Accepted Answer · answered Oct 27 '16 at 07:39

0

Your result is from mysqli_query while you are trying to fetch it using mysql_fetch_array. Try using mysqli_fetch_array for fetching the result.

But it will be a better if you use your DB class (the same that you are using for `$dbcnx->query) for fetching the result, or if this class doesn't have such method you can add it.

answered Oct 27 '16 at 07:39

krasipenkov

2,031
1
11
13

Thanks! I would never have noticed it! Is it possible that there is some documentation about the difference in mysql vs mysqli fetch array? – Specs Oct 27 '16 at 07:52
Look here http://php.net/manual/en/book.mysqli.php and here http://php.net/manual/en/book.mysql.php. This is also helpful: http://stackoverflow.com/questions/548986/mysql-vs-mysqli-when-using-php – krasipenkov Oct 27 '16 at 07:56

PHP var_dump NULL error after SQL Query

1 Answers1