I am writing a script to update a database. Part of the update checks for a duplicate stock number and I want to redirect back to the input form if there is a duplicate. If there is no duplicate, send the user off to another script to finish up the process.

Here is the code I am using:

PHP Code:

 //sql check routine
 //check for duplicates in database by stock number
 session_start();
 unset($_SESSION[error]);
 require_once("database.php");
 $stock_num=$_POST[stock_num];
 $_SESSION[stock_num]=$stock_num;
$sql="SELECT * FROM vehicles where stock_num = '$stock_num'";
$result=mysql_query($sql) or die(mysql_error());
if (mysql_num_rows($result)!=0){
    //There is a duplicate stock number so go back to form with an error
    $_SESSION[error]="There is a duplicate";
    }
    if ($_SESSION[error]){
    header("Location: newad.php");
    }

else {
header("Location: preview_text.php");
 } 


No matter what the results of my query, the next script called is always preview_text.php. What am I doing wrong?

Problem solved and had nothing at all to do with the header() function. It was my query! Funny how you can't satisfy an "if" when you never satisfy the conditions!

Again you select * just to get the number of records. You should select count(*) instead.