Cannot get SHA1,MD5 verifications to work if not uploading source image

	//Get SHA1 Hash.
	
	//Check if this value is actually uploaded.
	if (array_key_exists("HashCodeSHA_1", $_POST))
	{
		$postedSHA1Hash = $_POST ["HashCodeSHA_1"];

		//Compute SHA1 hash. Since Image Uploader sends the hash value encoded with Base 64 algorithm
		//the result should be also encoded with Base 64.
		$actualSHA1Hash = base64_encode(pack("H*",sha1_file($_FILES["SourceFile_1"]['tmp_name'])));
		
		//If the result differs from the uploaded one, the upload should be interpreted as corrupted.
		if ($postedSHA1Hash != $actualSHA1Hash)
		{
			header("HTTP/1.0 400 Bad Request");
			return;
		}
	}

	//Get MD5 hash.

	//Check if this value is actually uploaded.
	if (array_key_exists("HashCodeMD5_1", $_POST))
	{
		$postedMD5Hash = $_POST ["HashCodeMD5_1"];

		//Compute MD5 hash. Since Image Uploader sends the hash value encoded with Base 64 algorithm
		//the result should be also encoded wi	th Base 64.
		$actualMD5Hash = base64_encode(pack("H*",md5_file($_FILES["SourceFile_1"]['tmp_name'])));

		//If the result differs from the uploaded one, the upload should be interpreted as corrupted.
		if ($postedMD5Hash != $actualMD5Hash)
		{
			header("HTTP/1.0 400 Bad Request");
			return;
		}
	}

		if (array_key_exists("HashCodeSHA_1", $_POST))
		{
			$postedSHA1Hash = $_POST ["HashCodeSHA_1"];

		//Compute SHA1 hash. Since Image Uploader sends the hash value encoded with Base 64 algorithm
		//the result should be also encoded with Base 64.
			$actualSHA1Hash = base64_encode(pack("H*",sha1_file($_FILES['Thumbnail1_1']['tmp_name'])));
		
		//If the result differs from the uploaded one, the upload should be interpreted as corrupted.
			if ($postedSHA1Hash != $actualSHA1Hash)
			{
				header("HTTP/1.0 400 Bad Request");
				return;
			}
		}
		if (array_key_exists("HashCodeMD5_1", $_POST))
		{
			$postedMD5Hash = $_POST ["HashCodeMD5_1"];

		//Compute MD5 hash. Since Image Uploader sends the hash value encoded with Base 64 algorithm
		//the result should be also encoded wi	th Base 64.
			$actualMD5Hash = base64_encode(pack("H*",md5_file($_FILES['Thumbnail1_1']['tmp_name'])));

		//If the result differs from the uploaded one, the upload should be interpreted as corrupted.
			if ($postedMD5Hash != $actualMD5Hash)
			{
				header("HTTP/1.0 400 Bad Request");
				return;
			}
		}