PHP ob_flush() Function: Everything You Need to Know

As a PHP developer, you may need to flush the output buffer to send data to the client immediately rather than waiting for the buffer to fill up. The ob_flush() function is a built-in function in PHP that allows you to flush the output buffer. In this article, we will take an in-depth look at the ob_flush() function and its usage.

What is the ob_flush() Function?

The ob_flush() function is a PHP built-in function that allows you to flush the output buffer. Note that output buffering must be enabled with ob_start() before ob_flush() can be used. Additionally, ob_flush() only clears the PHP buffer; to actually send the data to the client, you typically need to call flush() afterward to clear the web server's buffer.

How to Use the ob_flush() Function

Using the ob_flush() function is straightforward. Here is the syntax of the function:

The PHP syntax of ob_flush() Function

ob_flush();

Here is an example of how to use the ob_flush() function to flush the output buffer:

How to Use the ob_flush() Function?

<‌?php
ob_start(); // Enable output buffering
echo "This will be buffered";
ob_flush(); // Flush PHP buffer
flush();    // Flush web server buffer
?>

In this example, we enable output buffering with ob_start(), output a message, and then use ob_flush() followed by flush() to send the message to the client immediately. Note that server-side buffering (e.g., in Apache or Nginx) may still delay delivery unless configured to allow immediate flushing.

Conclusion

The ob_flush() function is a useful tool for flushing the output buffer in your PHP web application. By understanding that it requires ob_start() to be enabled and is typically paired with flush() to bypass server buffers, you can reliably send data to the client immediately rather than waiting for the buffer to fill up. We hope this article has been informative and useful in understanding the ob_flush() function in PHP.

Practice

What does the PHP flush() function do?

It stops the execution of the current script.It pushes current output to the client without having to wait for the script to end.It deletes all variables and data in the current function.It allows to force the completion of any pending output and helps to free up memory.It returns the current date and time.