致命错误：调用未定义的函数mssql_query（）[重复]

Having this error when trying to query an INSERT, I have to to run when a Submit button is clicked.

<?php
if(isset($_POST['newPartbtn'])){
  $result = mssql_query("INSERT INTO Parts (PartNumber) VALUES ('2222')");
  if($result)
  {
    echo "Success";
  }
  else
  {
    echo "Error";
  }
}
?>

New to PHP so sorry if this is basic!

Here is my code to connect,

<?php
  $serverName = "Server";

  $connectionInfo = array( "Database"=>"Database");
  $conn = sqlsrv_connect( $serverName, $connectionInfo);

  if( $conn ) {
       echo "Connection established.<br />";
  }else{
       echo "Connection could not be established.<br />";
       die( print_r( sqlsrv_errors(), true));
  }
  ?>

</div>

First call for a new connection

      <?php
      if(isset($_POST['newPartbtn'])){
      $conn = mssql_connect('KALLESPC\SQLEXPRESS', 'sa', 'phpfi');
      $sql = mssql_query("INSERT INTO Parts (PartNumber) VALUES ('2222')");
      if($result)
      {
      echo "Success";
      }
      else
       {
       echo "Error";
       }
       }
       ?>