Error running SQL query in PHP

Question

I am fairly new to php and learning how to run sql queries using php.

So far I wrote following code:

    <?php
      $servername="localhost";
      $user="root";
      $password="mypassword";
      $dbname="mydbname";
      
      //Create Connection
      $conn=mysqli_connect($servername,$user,$password,$dbname);
      
      
      //Check connection
      if(!$conn)
        {
            die("connection failed" . mysqli_connect_error());
        }
        
        echo "<b>Connection is Successfull.</b>";
        
            
            mysqli_close($conn);
            unset($conn);
            $sql = "SELECT * FROM users";

            $query=mysqli_query($conn, $sql) or die(mysql_error())
        
        ?>

When I run above code, it gives me following error

Connection is Successful.

Notice: Undefined variable: conn in /index2.php on line 34

Warning: mysqli_query() expects parameter 1 to be mysqli, null given in index2.php on line 34

I have tried several other methods but all shows some kind of error.

Because you unset or close connection before your query execute `mysqli_close($conn); unset($conn);` add this at the end of your query — Saty, Dec 15 '15 at 06:15
You are closing mysql connection before query execution. Use `mysqli_close($conn); unset($conn);` after query execution or at the end of the file. — Apb, Dec 15 '15 at 06:17
Note - since your are using `mysqli` and not `mysql`, your `or die(mysql_error())` should be `or die(mysqli_error($conn))` — Sean, Dec 15 '15 at 06:18

Marcus · Answer 1 · 2015-12-15T06:21:49.627

0

You close your connection before sending the query. Uncool :)

Move

mysqli_close($conn);
unset($conn);

below

$sql = "SELECT * FROM users";
$query=mysqli_query($conn, $sql) or die(mysql_error())

edited Dec 15 '15 at 06:21

answered Dec 15 '15 at 06:17

Marcus

1,910
2
16
27

Better use "below" instead of "behind". – Tᴀʀᴇǫ Mᴀʜᴍᴏᴏᴅ Dec 15 '15 at 06:19
1

I've changed it, thanks :) – Marcus Dec 15 '15 at 06:22

score 0 · Answer 2 · edited Dec 15 '15 at 08:40

You can't close mysqli connection before query execution.

You have to close connection when all queries executed.

<?php
      $servername="localhost";
      $user="root";
      $password="mypassword";
      $dbname="mydbname";

      //Create Connection
      $conn=mysqli_connect($servername,$user,$password,$dbname);


      //Check connection
      if(!$conn)
        {
            die("connection failed" . mysqli_connect_error());
        }

        echo "<b>Connection is Successfull.</b>";



            $sql = "SELECT * FROM users";

$query=mysqli_query($conn, $sql) or die(mysql_error())
mysqli_close($conn);
            unset($conn);
        ?>

NormundsP · Answer 3 · 2015-12-18T14:46:50.817

0

For example:

//mysql configuration
     $server = "localhost";
     $dbuser = "root";
     $dbpw = "";
     $db = "db";
     $con = "";
     $con = new mysqli($server,$dbuser,$dbpw, $db);
 //get data from table   
        $sql = "SELECT * FROM users";
            $rs=$con->query($sql);
            while($row = $rs->fetch_assoc()){
    echo $row['ID'];
    }

edited Dec 18 '15 at 14:46

answered Dec 15 '15 at 06:21

NormundsP

445
2
7
16

score -1 · Answer 4 · answered Dec 15 '15 at 06:20

-1

$sql = "SELECT * FROM users";
$query=mysqli_query($conn, $sql) or die( mysqli_error($conn));
mysqli_close($conn);
unset($conn);

answered Dec 15 '15 at 06:20

Shailesh Katarmal

2,757
1
12
15

Either provide some text explaining what your code does, or leave comments in the code itself. – Sergey Telshevsky Dec 15 '15 at 06:54

Error running SQL query in PHP

4 Answers4