How to detect if headers are already sent in PHP
I’m sure most of us have encountered the following error message while playing with the header function in PHP
“Cannot modify header information – headers already sent by …â€?
How can we detect whether the script has already sent out headers? PHP has a function headers_sent() which allows you to check if the headers are already sent out before you take any action. Here’s how you could use the function in your code:
if(headers_sent())
{ //if headers already sent out print some message.
echo "Please go to yahoo.com";
}
else{
//send the user automatically to test.php
header('Location: http://yahoo.com');
}
The code above checks to see if PHP has already sent out headers anywhere else. If so, the script will print a message on screen, else the user is automatically redirected to the yahoo.com.
better:
function safeRedirect($url) {
if(headers_sent()) {
echo “Please go to “.$url.”“;
echo “\n”;
echo “window.location.href=’”.$url.”‘;\n”;
echo “\n”;
echo “\n”;
echo “\n”;
}
else{
header(‘Location: ‘.$url);
}
exit;
}
Don’t forget the closing ‘exit’, otherwise the script will continue executing.