PHP headers_sent()Function
Complete PHP HTTP Reference Manual
Definition and Usage
The headers_sent() function checks whether HTTP headers have been sent/where they have been sent.
If the headers have been sent, this function returns TRUE; otherwise, it returns FALSE.
Syntax
headers_sent(file,line)
| Parameters | Description |
|---|---|
| file,line | Optional. If the file and line parameters are set, headers_sent() will store the PHP source filename and line number where the output started in the file and line variables. |
Tips and Notes
Note:Once the header block has been sent, you cannot use the header() function to send other headers.
Note:The optional file and line parameters are new in PHP 4.3.
Example 1
<?php
// If no headers are sent, send one
if (!headers_sent())
{
header("Location: http://www.w3cschool.cc/");
exit;
}
?>
<html>
<body>
...
...
// If no headers are sent, send one
if (!headers_sent())
{
header("Location: http://www.w3cschool.cc/");
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.w3cschool.cc/");
exit;
// Trigger an error here
}
else
{
echo "Headers sent in $file on line $line";
exit;
}
?>
<html>
<body>
...
...
// $file and $line are passed in for later use
// Do not assign them values beforehand
if (!headers_sent($file, $line))
{
header("Location: http://www.w3cschool.cc/");
exit;
// Trigger an error here
}
else
{
echo "Headers sent in $file on line $line";
exit;
}
?>
<html>
<body>
...
...
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