In what scenarios or use cases is the flush() function in PHP most commonly utilized?

The flush() function in PHP is commonly used when you want to send output to the browser before the script has finished executing. This can be useful when you have a long-running script or when you want to show progress to the user as the script is running. By using flush(), you can send output to the browser immediately without waiting for the script to finish.

<?php
// Start output buffering
ob_start();

// Send some initial output to the browser
echo "Processing...";

// Flush the output buffer
flush();

// Simulate a long-running task
sleep(2);

// Send more output to the browser
echo "Task completed.";

// Flush the output buffer again
flush();

// End output buffering and send everything to the browser
ob_end_flush();
?>