Fatal error: call to a member function query() on null in

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I have an errors it says

Notice: Undefined variable: mysqli in C:\xampp\htdocs\cwang\users.php on line 40

Fatal error: Call to a member function query() on null in C:\xampp\htdocs\cwang\users.php on line 40

What I have tried:

dbconnect.php

<?php


$con = mysqli_connect("localhost","root","","dbmargs");

if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
?>

user.php

<html>

<head>

  <style>
			body
				{
					background-image: url('img/indexback.jpg');
					background-attachment: fixed;
					background-size: 100% 100%;
				}
		</style>

<title>MySQLi Read Records</title>
 <link rel="stylesheet" type="text/css" href="css/style.css">
</head>

<body>

<ul class="topnav">

    <li><a href="#home">Home</a></li>



</ul>

<?php


include 'dbconnect.php';



$query = "select * from tblregister";


$result = $mysqli->query( $query );



$num_results = $result->num_rows;



echo "<div><a href='add.php'>Create New Record</a></div>";

if( $num_results > 0){ 

echo "<table border='1'>";



echo "<tr>";

echo "<th>Firstname</th>";

echo "<th>Lastname</th>";

echo "<th>Username</th>";

echo "<th>Action</th>";

echo "</tr>";



while( $row = $result->fetch_assoc() ){



extract($row);



echo "<tr>";

echo "<td>{$firstname}</td>";

echo "<td>{$lastname}</td>";

echo "<td>{$username}</td>";

echo "<td>";

//just preparing the edit link to edit the record

echo "<a href='edit.php?id={$id}'>Edit</a>";

echo " / ";



echo "<a href='#' onclick='delete_user( {$id} );'>Delete</a>";

echo "</td>";

echo "</tr>";

}

echo "</table>";//end table

}else{

//if database table is empty

echo "No records found.";

}

//disconnect from database

$result->free();

$mysqli->close();

?>

</body>

</html>

Posted 6-Mar-17 19:25pm

Jim Clinton

Updated 9-Dec-19 1:21am

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Jochen Arndt · Answer 1 · 2017-03-07T00:02:00

You are mixing the object oriented and the procedural style when executing mysqli functions. I suggest to choose only one style.

dbconnect.php uses the procedural style and assigns the object to $con.

In user.php you are calling the query function in the object oriented style using the undefined $mysqli object:

PHP

$result = $mysqli->query( $query );

You must use the object returned from connecting instead:

PHP

$result = $con->query( $query );

or use the procedural style:

PHP

$result = mysqli_query( $con, $query );

See also the examples at PHP: mysqli::query - Manual[^].