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PHP Error: Cannot Modify Header Information
Let’s dive into a common hiccup you might encounter on your PHP journey, especially when using the Symfony framework. Have you ever come across this pesky error: PHP Error: Cannot Modify Header Information? 🤔 If yes, you’re not alone. If not, well, consider this your heads-up because it’s quite the rite of passage in the world of PHP.
What’s This Error About?
In simple terms, PHP is telling you, “Hey, I was about to send the webpage to the browser, but something came up that made me change the headers of the page, and I can’t do that once I’ve started sending the page.” It’s like trying to change the destination after your spaceship has already launched. 🚀
Headers are parts of the response sent back to your browser to tell it how to handle the page. For example, they can instruct the browser to treat the response as an HTML page, a PDF, or even as a file to download. Changing them midway is a no-go.
Common Causes
- Output Before Headers: The most common trigger for this error is attempting to modify headers after sending output to the user. Even a single whitespace or an unnoticed echo can cause this.
- Cookies and Sessions: Trying to set cookies or start a session after output has been sent is another common cause. PHP…
