PHP / MySql changes to existing code

QUERY 1 The following script updates an on-line form. This form contains file-type entries (1 picture and 2 PDFs') and text entries. A. In the following PHP code, what changes need to be made in order NOT to update FILE-TYPE entries when MySql corresponding fields already contains a prior entry (or is not empty in other words)? B. In the following same PHP code, what changes need to be made in order to update a TEXT entry when MySql corresponding fields already contains a prior entry and the user later clears the TEXT input field after having already saved a prior entry in the form. <?php foreach ($_POST as $key => $val) { $_POST[$key]=filter_input(INPUT_POST, $key, FILTER_SANITIZE_SPECIAL_CHARS);} include("[login to view URL]"); $bouton='Submit'; $uniqueid=$_POST["email_address"]; $photocheck=$_POST["photo"]; $image=$_FILES['photo']['name']; $image2 = "$uniqueid$image"; move_uploaded_file($_FILES["photo"]["tmp_name"], "upload/" . $image2); $divorce=$_FILES['divorce_order']['name']; $divorce2 = "$uniqueid$divorce"; move_uploaded_file($_FILES["divorce_order"]["tmp_name"], "upload/" . $divorce2); $marriagecertificate=$_FILES['marriage_certificate']['name']; $marriagecertificate2 = "$uniqueid$marriagecertificate"; move_uploaded_file($_FILES["marriage_certificate"]["tmp_name"], "upload/" . $marriagecertificate2); $recu=$_POST; $titre=""; $contenu=""; $reqComplete=""; foreach ($recu as $titre => $contenu) { $contenu=trim(addslashes($contenu)); if($titre!=$bouton AND $contenu!="") { $reqComplete.=$titre."='$contenu', "; } } $reqComplete=rtrim($reqComplete, ", "); $conn = mysql_connect("localhost","epermit_martin","xxxxxxxxxxxx") or die("Could not connect to database"); $rs = mysql_select_db("epermit_immigDB",$conn) or die ("Could not select database"); $requete="UPDATE form1738 SET $reqComplete where email_address = \"$email_address\""; $resultat=mysql_query($requete) or die ("Invalid request : <br /> ".mysql_error()); $requete="select max(idimmigDB) from form1738"; $rs= mysql_query($requete,$conn); $row=mysql_fetch_row($rs); $_SESSION[id]=$row[0]; #insert picture in db with unique identifier $sql2 = "update form1738 set photo = \"$image2\" where email_address = \"$email_address\""; $rs2 = mysql_query ($sql2) or die ("Invalid request : <br /> ".mysql_error()); #insert pdfs in db with unique identifier $sql3 = "update form1738 set divorce_order = \"$divorce2\" where email_address = \"$email_address\""; $rs3 = mysql_query ($sql3) or die ("Invalid request : <br /> ".mysql_error()); $sql4 = "update form1738 set marriage_certificate = \"$marriagecertificate2\" where email_address = \"$email_address\""; $rs4 = mysql_query ($sql4) or die ("Invalid request : <br /> ".mysql_error()); mysql_close($conn); header("location:[login to view URL]"); ?> QUERY 2 How to generate an access code which customers must buy on-line in order for them to access and use the website, [login to view URL] QUERY 3 Is this an appropriate time-out script? <?php session_start(); # Check for session timeout, else initiliaze time if (isset($_SESSION['timeout'])) { # Check Session Time for expiry # # Time is in seconds. 10 * 120 = 1200s = 20 minutes if ($_SESSION['timeout'] + 10 * 120 < time()){ session_destroy(); header("Location: [login to view URL]"); } } else { # Initialize time $_SESSION['timeout']=time(); } ?>