As mbrugue sugest, the second parameter can also be use to save an animated gif:
<?php
$anim = new Imagick();
$files = scandir($myFramesPath);
foreach( $files as $f )
{
$auxIMG = new Imagick();
$auxIMG->readImage($mytifspath.$f);
$anim->addImage($auxIMG);
}
//write animated gif
$anim->writeImages('anim.gif', true);
?>