system/HTTP/Files/FileCollection.php
public function hasFile(string $fileID): bool
	{
		$this->populateFiles();

		if (strpos($fileID, '.') !== false)
		{
			$segments = explode('.', $fileID);

			$el = $this->files;

			foreach ($segments as $segment)
			{
				if (! array_key_exists($segment, $el))
				{
					return false;
				}

				$el = $el[$segment];
			}

			return true;
		}

		return isset($this->files[$fileID]);
	}
public function hasFile(string $fileID): bool
	{
		$this->populateFiles();

		if (strpos($fileID, '.') !== false)
		{
			$segments = explode('.', $fileID);

			$el = $this->files;

			foreach ($segments as $segment)
			{
				if (! array_key_exists($segment, $el))
				{
					return false;
				}

				$el = $el[$segment];
			}

			return true;
		}

		return isset($this->files[$fileID]);
	}
Checks whether an uploaded file with name $fileID exists in
this request.

@param string $fileID The name of the uploaded file (from the input)

@return boolean