php incrementing while loop

$blanknumber = $_POST["blankstartnumber"];

while ($blanknumber <= ($_POST["blankendnumber"] ))
{    

echo "$blanknumber";
$blankid = $blanknumber;

$query = "INSERT INTO blank (Blank_ID) VALUES ('$blankid')";

mysql_query($query,$con);
$blanknumber++;

}

So the values are added into the database. Lets say if I have the starting number at 1 and ending at 5. It wi开发者_如何学Cll all the those values, but it's still trying to add more into the database. I also tried adding an IF statement aswell. if ($blanknumber != $_POST["blankendnumber"])

12345 Error: Duplicate entry '5' for key 'PRIMARY'

Make sure your $POST value is an integer; by default, I believe it will be cast as a string.

$_POST['varName'] = (int) $_POST['varName'];

edit:

$blanknumber = $_POST["blankstartnumber"];
while ($blanknumber <= ($_POST["blankendnumber"] ))

This should only execute once, since you're setting both comparison variables equal. Definitely 2x check your code.

The database error indicates that Blank_ID is your primary key for that table, and you'd already inserted a 5 into the row. A primary key's values can exist only once in the entire table - duplicates are forbidden (if they were allowed, it wouldn't be a primary key anymore).

If your while loop isn't ending, I'd suggest dumping out both the blankendnumber and blankstartnumber before the loop starts, making sure you've got the right values in there.

It looks like it's actually functioning properly, but you might not have tidy'ed up your db table prior to running. If your output was:

123455 Error: Duplicate entry '5'...

Then, you'd have a programming error, as 5 is getting run twice. Instead, I think you already have data in the blank table that causes a conflict.

Edit: to automatically have MySQL handle the duplicate key error gracefully, you can use the ON DUPLICATE KEY clause to update the row.

INSERT INTO blank (Blank_ID) VALUES (5) ON DUPLICATE KEY UPDATE mod_date = NOW();