mysql - Mysqli PHP Connection Fatal Error -

i trying create connection web form mysql database using php. code follows:

connection.php:

<?php $link = mysqli_connect("", "", "", "");  if (!$link) { echo "error: unable connect mysql." . php_eol; echo "debugging errno: " . mysqli_connect_errno() . php_eol; echo "debugging error: " . mysqli_connect_error() . php_eol; exit; }  echo "success: proper connection mysql made! my_db database great." . php_eol; echo "host information: " . mysqli_get_host_info($link) . php_eol;  phpinfo(); 

this part seems work.. connects thank you.php:

<?php  function connect()     {         $conn = mysqli_connect("", "", "", "");     }  ini_set('display_errors', 1); error_reporting(~0);  require 'connection.php'; $conn    = connect(); $query   = mysqli_query($conn,"insert members (username) values('1111username')"); $success = $conn->query($query);  if (!$success) { die("couldn't enter data: ".$conn->error);  }  echo "thank contacting <br>";  mysqli_close($conn);  ?> 

i getting following errors:

warning: mysqli_query() expects parameter 1 mysqli, null given in /var/sites/i/site/public_html/contactform/thankyou.php on line 15

fatal error: call member function query() on null in /var/sites/i/site/public_html/contactform/thankyou.php on line 16

there several issues script:

1: need return connection likes o:

function connect() {     return mysqli_connect("", "", "", ""); } 

2: when run

$query   = mysqli_query($conn,"insert members (username) values('1821username')"); 

you have executed sql db, not need $success = $conn->query($query);

so code should be:

<?php  function connect()     {         return mysqli_connect("", "", "", "");     }  ini_set('display_errors', 1); error_reporting(~0);  require 'connection.php'; $conn    = connect(); $query   = mysqli_query($conn,"insert members (username) values('1821username')");  if (!$query) { die("couldn't enter data: ".$conn->error);  }  echo "thank contacting <br>";  mysqli_close($conn);  ?>