PHP headers_sent() Function
❮ Complete PHP HTTP Reference
Definition and Usage
The headers_sent() function checks if / where the HTTP headers have been sent.
This function returns TRUE if headers has been sent or FALSE if not.
Syntax
headers_sent(file,line)
| Parameter | Description |
|---|---|
| file,line | Optional. If the file and line parameters are set, headers_sent() will put the PHP source file name and line number where output started in the file and line variables |
Tips and Notes
Note: You can't add more header lines using header() once the header block has already been sent.
Note: The optional file and line parameters were added in PHP 4.3.
Example 1
<?php
// If no headers are sent, send one
if (!headers_sent())
{
header("Location: https://www.w3schools.com/");
exit;
}
?>
<html>
<body>
...
...
Example 2
Using the optional file and line parameters:
<?php
// $file and $line are passed in for later use
// Do not assign them values beforehand
if (!headers_sent($file, $line))
{
header("Location: https://www.w3schools.com/");
exit;
// Trigger an error here
}
else
{
echo "Headers sent in $file on line $line";
exit;
}
?>
<html>
<body>
...
...
❮ Complete PHP HTTP Reference
