How to Fix PHP Header Redirect Failures: Common Causes and Practical Solutions

What Is PHP Header Redirect?

In PHP development, the header() function is commonly used to perform page redirects. After calling header(), the server sends an HTTP response header instructing the browser to redirect. For example:

<span class="fun">header("Location: http://www.example.com");</span>

If used improperly, this can cause redirect failures that affect user navigation.

Common Causes of PHP Header Redirect Failures

Premature Output Causes Redirect Failure

No output (including whitespace or HTML tags) should be sent before calling header(). Once the browser receives any part of the response headers, further redirects will fail.

Improper Use of exit() or die()

Calling exit() or die() immediately after header() is a common practice to stop script execution and ensure redirect occurs. However, misuse may prevent necessary code from running, causing unexpected issues.

Incorrect HTTP Status Code

Sometimes it is necessary to explicitly specify the HTTP status code (such as 302 for redirection) to ensure the browser correctly processes the redirect. For example:

<span class="fun">header("Location: http://www.example.com", true, 302);</span>

Practical Solutions

Avoid Any Output Before header()

Make sure no output is sent before calling header(). It is recommended to keep all code within PHP tags to avoid accidental whitespace or new lines:

<?php
// No output here
header("Location: http://www.example.com");
exit();
?>

Use Output Buffering

If output before header() is necessary, enable output buffering to hold output temporarily until redirect:

<?php
ob_start();
// Output is allowed here
header("Location: http://www.example.com");
ob_end_flush();
?>

Check Error Logs

If the redirect still fails, reviewing server error logs can help identify specific issues and speed up troubleshooting.

Summary

PHP header redirect failures are usually caused by premature output, missing or incorrect status codes, or interrupted script execution. By properly using the header() function, setting the correct status codes, and employing output buffering, these problems can be effectively resolved, improving user experience.