You are trying to send an HTTP header or cookie using header() or setcookie(), but PHP reports a “headers already sent” error message.
This error happens when you send nonheader output before calling header() or setcookie().
Rewrite your code so any output happens after sending headers:
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<?php // good setcookie("name", $name); print "Hello $name!"; // bad print "Hello $name!"; setcookie("name", $name); // good setcookie("name",$name); ?> <html><title>Hello</title> |
An HTTP message has a header and a body, which are sent to the client in that order.
Once you begin sending the body, you can’t send any more headers. So if you call setcookie() after printing some HTML, PHP can’t send the appropriate Cookie header.
Also, remove trailing whitespace in any include files. When you include a file with blank lines outside <?php ?> tags, the blank lines are sent to the browser.
Use trim() to remove leading and trailing blank lines from files:
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$file = '/path/to/file.php'; // backup copy($file, "$file.bak") or die("Can't copy $file: $php_errormsg"); // read and trim $contents = trim(join('',file($file))); // write $fh = fopen($file, 'w') or die("Can't open $file for writing: $php_errormsg"); if (-1 == fwrite($fh, $contents)) { die("Can't write to $file: $php_errormsg");} fclose($fh) or die("Can't close $file: $php_errormsg"); |
Instead of processing files on a one-by-one basis, it may be more convenient to do so on a directory-by-directory basis.
Another perfectly legitimate approach to ensuring included files don’t have any trailing whitespace is to just leave off the closing ?> tag.
If the included file is purely PHP, this method guarantees that you won’t have to go back to that file to clean up inadvertent whitespace.
