Query returns bool(false)

Question

I am a beginner regardig to PHP and trying to learn it. My boolean returns false and I can't find the answer how to solve this. Thank you!

            $leden_id = $_POST["leden_id"];

            $connect = mysqli_connect("localhost", "root", "root", "bibliotheek");
            $ophalen = "SELECT naam FROM leden WHERE leden = " . $leden_id . ";";
            $r = mysqli_query($connect, $ophalen);
            var_dump($r);

please use `error_reporting(E_ALL); ini_set('display_errors', 1);` on top of your page and let us know what error occurs. Make sure that `$leden_id` is not empty. correct `$ophalen = "SELECT naam FROM leden WHERE leden = " . $leden_id . ";";` to `$ophalen = " SELECT naam FROM leden WHERE leden ='$leden_id' ";` Plus : you should **really** consider using [PPS : Prepared Parameterized Statements](http://php.net/manual/en/mysqli.quickstart.prepared-statements.php). This will help [Preventing SQL injection](http://stackoverflow.com/questions/60174/how-can-i-prevent-sql-injection-in-php) — OldPadawan, Apr 18 '17 at 06:59

score 0 · Answer 1 · answered Apr 18 '17 at 06:59

check this and not tested change

 $ophalen = "SELECT naam FROM leden WHERE leden = " . $leden_id . ";";

to

$ophalen = "SELECT naam FROM leden WHERE leden = '" . $leden_id . "'";

if your post value fine then check this

 $leden_id = $_POST["leden_id"];

 $connect = mysqli_connect("localhost", "root", "root", "bibliotheek");
 $ophalen = "SELECT naam FROM leden WHERE leden = '" . $leden_id . "'";
 $r = mysqli_query($connect, $ophalen);
 var_dump($r);

score 0 · Answer 2 · answered Apr 18 '17 at 07:00

You have an error with $ophalen value, your code is not properly closing the query with single and double quotes. Also, keep in mind to check for SQL injections.

Replace your code to:

 $leden_id = $_POST["leden_id"];

 $connect = mysqli_connect("localhost", "root", "root", "bibliotheek");
 $ophalen = "SELECT naam FROM leden WHERE leden = '" . $leden_id . "'";
 $r = mysqli_query($connect, $ophalen);
 var_dump($r);

score 0 · Accepted Answer · answered Apr 18 '17 at 07:02

Apart from the common SQL injection problem, let me give you some pointers on debugging:

$ophalen    =    "SELECT naam FROM leden WHERE leden = '" . $leden_id . "'"; // Change this line
$r          =    mysqli_query($connect, $ophalen) or die (mysqli_error($connect)); // Check for errors

score 0 · Answer 4 · answered Apr 18 '17 at 07:10

Thank you all for helping! I will prevent SQL injections, it won't be used for an actual website it's an assignment I use for practicing.

I used

or die (mysqli_error($connect));

and found this error popped up "Unknown column 'leden' in 'where clause'" So I have to look again at my database.

Thanks!

Query returns bool(false)

4 Answers4