What do I do when I receive a PHP header error message?

Error Messages:

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/content/u/s/e/username/html/file.php:2) in /home/content/u/s/e/username/html/file.php on line 3

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/content/u/s/e/username/html/file.php:2) in /home/content/u/s/e/username/html/file.php on line 3

Warning: Cannot modify header information - headers already sent by (output started at /home/content/u/s/e/username/html/file.php:2) in /home/content/u/s/e/username/html/file.php on line 4

Cause:

This error is caused if the your PHP scripts are printing to the browser prior to sending headers. A common example is printing the html tags prior to starting a session, or setting a cookie. The error tells the line that needs to be altered (in this case, it is on /file.php line 2).

Resolution:

To resolve this error remove the lines from the PHP code that are printing to the browser prior to sending headers.

Another common cause for this error is white space either at the beginning or end of the file. The fix is to remove that whitespace from the file. Read the error message carefully. It says output started at ... followed by a file name and a line number. That is the file (and line) that you need to edit. Ignore the second file name - that is only a file that included the file that has the whitespace. The first file is the one you have to edit, not the second one.