( PEAR::SWF ) File_SWF which inherits from PEAR package, allows operations I/O on swf files.
Basically, other than returning all the main information from an swf file, such as the bg color, framerate, player version, compression, protection used, movie size.. it allows to modify some of those parameters.
For example it can change the framerate, background, protection.

An Example:

<?php
 // include the PEAR package
 require "File/SWF.php";
 $flash = new SWF("source.swf");
 if($flash->is_valid()){
    $stat = $flash->stat();
    // this give all the info
    // and also..
    $fps = $flash->getFrameRate();
    $size = $flash->getMovieSize();
    $bg = $flash->getBackgroundColor();
    $prot = $flash->getProtected();
    $compr = $flash->getCompression();
    $version = $flash->getVersion();

    // they can be changed...
    $flash->setFrameRate(60);
    $flash->setProtected(1);
    $flash->setBackgroundColor(51,51,204);
    $flash->setCompression(1);

    // and write a new file...
    $flash->write("./new_one.swf",1);
 }
?>

Here the source file: File_SWF