uploadify saving results in database - php

Question

I am new to PHP. here is my code to save results of form to database and uploaded file name.I am using uploadify to upload files.
Here i have 2 problems.
file saves on its location in mozila but do not works for chrome.
coded goes here.
if (!empty($_FILES)) {
$tempFile = $_FILES['Filedata']['tmp_name'];
$picAd= $_FILES ['Filedata']['name'];
// to change same file name
$picAd=rand(0,1000)."_".rand(0,1000)."_".$picAd;
$targetPath = $_SERVER['DOCUMENT_ROOT'] . $_REQUEST['folder'] . '/';
// this line works ok for all browsers
$targetFile = str_replace('//','/',$targetPath) . $_FILES['Filedata']['name'];
this line not works for chrome
// $targetFile = str_replace('//','/',$targetPath) . $picAd; <<Error for chrome
if( move_uploaded_file($tempFile,$targetFile)){ // 4
echo true;
}else{
echo false;
}
saving results to database .
static $picAd;
if(isset($_POST['submit'])){
// varibles
$uname=$_REQUEST['userName'];
$pw=$_REQUEST["pw"];
$email= $_REQUEST["email"];
$twit= $_REQUEST["twit"];
$user="user";
if($picAd != ""){
$q="insert into users values(Null,'$user','$uname','$pw','$email','$twit','$picAd')";
mysql_query($q);
mysql_close($dbc); }
}
Here i am not getting the value of $picAd in database its value goes NUll.