If searched number exists in MySQL database, go to a certain link
<?
$username="data";
$password="data1";
$database="data";

$TicketNumber=$_POST['TicketNumber'];

mysql_connect(localhost,$username,$password);
@mysql_select_db($database) or die( "Unable to select database");

$query="SELECT * FROM plate";
$result=mysql_query($query);

$num=mysql_numrows($result);

mysql_close();
?>

$username="data";
$password="data1";
$database="data";

$mysqli = new mysqli("localhost", $username, $password, $database);


// Do this if it's a string:
// $ticketNumber = $mysqli->real_escape_string($_POST['TicketNumber']);
// since it should be an int, we can do better:
$ticketNumber = intval($_POST['TicketNumber']);

$results = $mysqli->query("SELECT * FROM plate WHERE ticket_number = $ticketNumber");
if( ! $results->num_rows) {
  header("Location: /scriptC.php");
  die();
}
$ticket = $results->fetch_assoc();
$ticketTime = strtotime($ticket['date']);
$requestTime = strtotime($_POST['date']);

if(($requestTime - $ticketTime) < 72*60*60) {
  header("Location: /scriptA.php");
  die();
}
header("Location: /scriptB.php");
die();



$mysqli->close();

while($row = mysql_fetch_array($result))
  {
   if($row['ticketId'] == n)
       /* do the following */
  }

$query = "SELECT date, TicketNumber FROM invoices WHERE TicketNumber=";
$query = $query.$TicketNumber;
$result = mysql_query($query);
if(mysql_num_rows($result) == 0)
{
    // Do link C
}
while ( $row = mysql_fetch_array($result) )
{
    if ( calculate 72 hours against date in this row )
    {
        // Do stuff
    }
    else
    {
        // Do other stuff
    }
}

<?php
$username="data";
$password="data1";
$database="data";
mysql_connect(localhost,$username,$password);
@mysql_select_db($database) or die( "Unable to select database");

// get and 'validate" the ticketNumber
$ticketNumber = (isset($_POST['ticketNumber']) && is_numeric($_POST['ticketNumber'])) ? (int)$_POST['ticketNumber'] : 0;

// build the MySQL query selecting the number of days between today (NOW()) and the ticket's date
$sql = 'SELECT DATEDIFF(date, NOW()) AS daysElapsed FROM invoices WHERE TicketNumber = ' . $ticketNumber;
if (($result = mysql_query($query)) && (mysql_num_rows($result) > 0)) {
    // we only want a single row/ticket, so no need to loop
    $row = mysql_fetch_array($result);
    $location = '/link_b.php';
    if ($row[0] <= 3) {
        // less than 3 days, or 72 hours
        $location = '/link_a.php';
    }
    mysql_close();
    header('Location: ' . $location);
    die();
} else {
    header('Location: /link_c.php');
    die();
}

?>