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Editorial Team
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Asked: 2026-05-11T21:51:44+00:00

I’m a PHP virgin (first day), so please type slowly. I have a number

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I’m a PHP virgin (first day), so please type slowly.

I have a number of images, bg_001.jpg, bg_002.jpg, etc., which I want to rotate through each time the page is refreshed. I tried this:

if (isset($_COOKIE["bg1"])) {
  $img_no = $_COOKIE["bg1"] + 1;
} else {
  $img_no = 1;
}
$filename = 'bg_' . sprintf("%03d", $img_no) . '.jpg';
if (!file_exists("/img/" . $filename)) {
  $img_no = 1;
  $filename = 'bg_' . sprintf("%03d", $img_no) . '.jpg';
}
setcookie("bg1", $img_no, time() + 86400);
print '<img src="img/' . $filename . '" alt="" height="175" width="800"> ';

Instead of a cookie I get a 

Warning: Cannot modify header information - headers already sent by (output 
started at /home2/.../about.php:7) in /home2/.../about.php on line 31

Line 31 being the line with the setcookie. I already found pointers about PHP having trouble with Unicode’s BOM, but I have no idea how to fix it (if it is the problem here in the first place).
So, to make it official (and avoid a “not a real question” label), how do I fix this? 🙂

Constructive criticism on my code is welcome too.

epilogue:
Seemed like a common newbie error: several answers toward the same solution within fifteen minutes. Thanks guyz/galz.

So I moved everything except the print to the start of the file, and indeed: fixed.

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1 Answer

  1. Editorial Team

    cookies can only be sent, if there are no information sent prior. This means that the first thing in your PHP file has to be <?php, and nothing can get before that part (not even the dreaded UTF-8 BOM), because if something is before the first <?php (like <html>), then php will send those data for the browser and after data is sent you can’t use setcookie. Refactor your code to look something like this:

    <?php
 (...)
 setcookie(...)
 (...)
?>
<HTML>
(...)
</HTML>

    And double check that editors like notepad didn’t put any UTF-8 BOM signatures before the first <?php in the file.

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