Call to undefined function mysql_query

Find here for installation guide on php.net

Assuming we have already installed/Configured MySQLi. Next, Lets see how can we perform the following in MySQLi

• Connect Mysql Database
• Query to Database tables

Below program demonstrates MySQLi with a prepared statement. Lets dive into code:

$host = "localhost"; // Specify your server Host/IP address
$username = "username"; // Replace your Database username here
$password = "password"; // Replace your Database password here
$db= "demo"; //Replace your database name here

$con = new mysqli($host, $username, $password, $db);


// Ensure if MySQLi connection works
if ($con->connect_error) {
  echo "Failed to connect Database: " . $con->connect_error; 
  exit;
}


$id = filter_var( $_POST['id'], FILTER_SANITIZE_NUMBER_INT);

$sql = "SELECT email, name FROM tbl_employee WHERE id =?"; // SQL with parameters
$stmt = $con->prepare($sql); 
$stmt->bind_param("i", $id);
$stmt->execute();
$result = $stmt->get_result(); // get the mysqli result

print_r($result ); // Added For demonstration purpose 

$user = $result->fetch_assoc(); // fetch data  

print_r($user); 

Explanation:

• new mysqli($servername, $username, $password, $db) Open database connection by passing required parameters to mysqli constructor.
• It's good practice to check whether a connection is successful before processing further query execution. Therefore using here $conn->connect_error to check if there is an error in the database connection.
• Assuming here that we received input data as id through the post method. Sanitizing received data (especially if it's user input) to filter out non-number values to avoid any malicious code.
• Prepare the desired query using the Mysqli prepare method. For demonstration purposes we are executing a query to fetch email & name from tbl_employee table having id matched with the receive post request. ? mark in the Prepared query is added that will be bound with mapping data.
• Mysqli execute method is further used to perform prepared query execution with a marker (?) replaced with a data value.
• Mysqli get_result method used to get prepared query execution results. If you print returned result it will constraints some information like field_count, num_rows, etc mysqli_result Object ( [current_field] => 0 [field_count] => 2 [lengths] => [num_rows] => 1 [type] => 0 )
• Next Mysqli method fetch_assoc is used here to get the result in associative array format. Example Array ( [email] => test@gmail.com [name] => test )