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PHP headers_sent() Function

PHP HTTP Reference 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 where 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>

...
...

PHP HTTP Reference Complete PHP HTTP Reference
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