The Infuriating Error: Cannot Modify Header Information – Headers Already Sent

The Infuriating Error: Cannot Modify Header Information – Headers Already Sent

Are you a website developer or administrator tired of encountering the “Cannot modify header information – headers already sent” error? This error occurs when a server sends HTTP headers to a web browser before the intended web page is displayed. The error message is infuriating and can be challenging to troubleshoot, leading to confusion and stress.

What Causes the “Cannot Modify Header Information – Headers Already Sent” Error?

The error message indicates that output, such as whitespace or text, was already sent to the browser before the PHP header function was called. This output can stem from a variety of sources, including:

1. The whitespace or characters before the opening PHP tag

Many developers unintentionally add whitespace or characters before the opening PHP tag, which can cause the error. It’s helpful to confirm that no characters or whitespace exist before the opening PHP tag.

2. Output before the header function call

If your code produces any output before the header function, it can cause the headers sent error message. This output can be whitespace or even a warning message. You need to ensure that there are no outputs generated before the header function call.

3. Character encoding

Another factor that can cause this error is the character encoding in the document. One can use BOM (byte order mark) when saving the file, extra characters that sometimes put encoding in the header, causing the headers to be sent.

How to Fix the “Cannot Modify Header Information – Headers Already Sent” Error

Now that you know what causes the headers sent error message, below are several ways on how to fix it:

1. Observe good coding practices

It is recommended to practice good coding skills to avoid the headers sent error. Ensure that the PHP code runs before any output is generated.

2. Check for whitespace and characters

It is essential to review the code for any white spaces and characters before the opening PHP tag. Remove all of them as they can trigger the headers sent error in PHP.

3. Turn on Output Buffering

This technique is useful when you want to output content while maintaining the flexibility of adding new headers. Output buffering enables you to store all the output in a buffer until you decide to send out HTTP headers. Use this technique to eliminate the headers sent error.

4. Use the “ob_start” Function

The “ob_start” function is used to start output buffering in PHP. The function can be used to block the output to the browser, giving you full control over the headers.

Conclusion

The headers sent error message is a frustrating issue that can occur when developing or managing a website. However, it can be quickly fixed by following the solutions mentioned above. Remember, it’s vital to adhere to good coding practices and observe any whitespace and characters before the opening PHP tag. By implementing the right techniques, you can eliminate the headers sent error message and run a seamless website.