How does the flush() function interact with output buffering in PHP, and what implications does this have for file uploads?

The flush() function in PHP forces any output in the buffer to be sent to the client immediately. This can be useful for displaying content progressively instead of waiting for the entire script to finish executing. When dealing with file uploads, using flush() can ensure that the progress of the upload is displayed to the user in real-time. 

<?php
ob_start();

// Process file upload
if ($_FILES['file']['error'] === UPLOAD_ERR_OK) {
    $destination = 'uploads/' . $_FILES['file']['name'];
    move_uploaded_file($_FILES['file']['tmp_name'], $destination);

    // Flush output to show upload progress
    echo 'Upload in progress...';
    flush();

    // Additional processing or redirect
}

ob_end_flush();
?>

Keywords

flush() output buffering file uploads PHP implications

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