Fix Headers already sent error in PHP

Posted by joan16v

No output before sending headers!
Functions that send/modify HTTP headers must be invoked before any output is made. summary ⇊ Otherwise the call fails:

Warning: Cannot modify header information – headers already sent (output started at script:line)

Some functions modifying the HTTP header are:

header / header_remove
session_start / session_regenerate_id
setcookie / setrawcookie
Output can be:


Whitespace before
The UTF-8 Byte Order Mark specifically
Previous error messages or notices

print, echo and other functions producing output
Raw sections prior <?php code.