# 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: http://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: http://www.w3schools.com/");
exit;
// Trigger an error here
}
else
{
echo "Headers sent in $file on line $line";
exit;
}
?>
<html>
<body>
...
...

Complete PHP HTTP Reference

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