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Checks if or where headers have been sent
Network Functions
PHP Manual

headers_sent

(PHP 4, PHP 5)

headers_sentChecks if or where headers have been sent

Description

bool headers_sent ([ string &$file [, int &$line ]] )

Checks if or where headers have been sent.

You can't add any more header lines using the header() function once the header block has already been sent. Using this function you can at least prevent getting HTTP header related error messages. Another option is to use Output Buffering.

Parameters

file

If the optional 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.

line

The line number where the output started.

Return Values

headers_sent() will return FALSE if no HTTP headers have already been sent or TRUE otherwise.

Changelog

Version Description
4.3.0 The optional file and line parameters were added.

Examples

Example #1 Examples using headers_sent()

<?php

// If no headers are sent, send one
if (!headers_sent()) {
    
header('Location: http://www.example.com/');
    exit;
}

// An example using the optional file and line parameters, as of PHP 4.3.0
// Note that $filename and $linenum are passed in for later use.
// Do not assign them values beforehand.
if (!headers_sent($filename$linenum)) {
    
header('Location: http://www.example.com/');
    exit;

// You would most likely trigger an error here.
} else {

    echo 
"Headers already sent in $filename on line $linenum\n" .
          
"Cannot redirect, for now please click this <a " .
          
"href=\"http://www.example.com\">link</a> instead\n";
    exit;
}

?>

Notes

Note:

Headers will only be accessible and output when a SAPI that supports them is in use.

See Also


Network Functions
PHP Manual