The “Headers already sent” error in PHP occurs when output is sent to the browser before the header()
function is called.
This can disrupt session management and redirect operations. Here’s a quick fix:
Step 1: Check for Output Before Headers
Ensure no output (such as echo statements or HTML) is sent before calling header()
:
PHP
<?php
// Correct: Header function called before any output
header("Location: /newpage.php");
exit;
?>
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Step 2: Remove Whitespace
Check for any accidental whitespace or new lines outside the <?php ?>
tags:
PHP
<?php
// Ensure no whitespace before or after PHP tags
?>
<!DOCTYPE html>
<html>
<head>
<title>Example</title>
</head>
<body>
<!-- Content -->
</body>
</html>
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Step 3: Use Output Buffering
If you need to send headers after some output, enable output buffering at the start of your script:
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PHP
<?php
ob_start(); // Start output buffering
header("Location: /newpage.php");
ob_end_flush(); // Send output buffer and turn off buffering
?>
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Conclusion
By following these steps, you can effectively resolve the “Headers already sent” error and ensure your PHP application handles redirects and sessions correctly.