php - How to fix mysqli_query() and mysqli_fetch_array() errors -

i'm trying make php script prints text file website on button click.

this code:

<?php     mysqli_connect("host", "username", "password", "dbname");     if (isset($_post['button'])) {         mysqli_query("select name,lastname users order rand()");         $name = null;         $lastname = null;         while ($row = mysqli_fetch_array()) {             $name = $row['name'];             $lastname = $row['lastname'];         }         echo '<p><small>output:</small></p><pre style="min-width:auto;display:table;">' . $name . '_' . $lastname . '</pre>format: <b>name_lastname</b> <span style="width:310px;">';     } ?> <form method="post">     <button type="submit" class="btn btn-default" name="button">button</button>     <br> </form> 

and error every time when button clicked:

anyone knows how fix this?

you need introduce database connection variable mysqli_* functions required, $con in modified script:

<?php     $con = mysqli_connect("host", "username", "password", "dbname") or die(mysqli_error($con));     if (isset($_post['button'])) {         $result = mysqli_query($con, "select name,lastname users order rand()");         $name = null;         $lastname = null;         while ($row = mysqli_fetch_array($result)) {             $name = $row['name'];             $lastname = $row['lastname'];         }         echo '<p><small>output:</small></p><pre style="min-width:auto;display:table;">' . $name . '_' . $lastname . '</pre>format: <b>name_lastname</b> <span style="width:310px;">';     } ?> <form method="post">     <button type="submit" class="btn btn-default" name="button">button</button>     <br> </form> 

in addition need pass result set identifier returned mysqli_query(), $result in case. can found @ w3schools.