I have a class (taken from the Google code section) for uploading a
file but I do not know how to use /  call it.

Here is the html form:

<form enctype="multipart/form-data" action="up.php" method="POST">
    <input type="hidden" name="MAX_FILE_SIZE" value="20000000" />
    <input name="userfile" type="file" value="" size="40"/>
&nbsp;<input type="submit" name="UploadImage" value="go" />
</form>

here is the code for the class which I have not been able to test but
I assume it's OK.

<?php
/**
* Base Upload Class
*
* Upload Class Used for Uploading all kinds of
* Files, can be extended to fit specific needs
*/
class Upload extends File {
	/**
	* @var string
	*/
	var $type;
	/**
	* @var string
	*/
	var $tmp_name;
	/**
	* @var int
	*/
	var $error;
	/**
	* @var int
	*/
	var $size;
	

	/**
	* Class Constructor
	*
	* Creates a upload object from form data
	*
	* @param mixed
	* @return NULL
	*/
	function Upload($data,
$directory='/home/richsnap/public_html/ecozenhtml/images/'){
		$this->filename = $data['name'];
		$this->type = $data['type'];
		$this->tmp_name = $data['tmp_name'];
		$this->error = $data['error'];
		$this->size = $data['size'];
		$this->directory = $directory;
	}

	/**
	* Checks the FILE data for and errors, overloads the Form CheckData
	* $acceptedTypes = array of acceptable file types
	* $max_size = int size of file in bytes
	* <code>
	* <?php
	* define(MAX_SIZE,1500000);
	* $image_types = array('image/jpeg','image/gif','image/png','image/pjpeg');
	* ?>
	* </code>
	* @param array, int in bytes
	* @return array
	*/
	function CheckData($acceptedTypes, $max_size){
		// Make sure that we have something to check first
		if ($this->filename != ''){
			Debug('CheckData(), Checking File data for errors.');
			// Check to see if the dirstory is writable
			if (!is_writable($this->directory)){
				// Try to make it writable
				$path = '';
				foreach( split('/', $this->directory) as $data ){
					$path .= $data . '/';
					if ( !file_exists($path) ){
						umask(000);
						mkdir($path,0775);
					}
				}
			}
			if (!is_writable($this->directory))
				$error = 'Directory is not writable, please check with the systems
administrator';
		
			// Check file types
			if (!in_array($this->type,$acceptedTypes))
				$error = 'This type of file is not permitted, Please try again';
			else if ($this->size == 0)
				$error = 'The filesize is zero, Please try again';
			else if ($this->size > $max_size)
				$error = 'The filesize is too large, ' . $max_size . ' bytes is
filesize limit, Please try again';
		}
		
		// Return the Errors
		return $error;
	}

	/**
	* Upload File
	*
	* Moves the file from its temp location and puts it into the directory that is set
	*
	* @return BOOL true/false if the item was uploaded successfully
	*/
	function UploadFile(){
		// Format the filename to make sure it is directory safe
		$this->FormatFilename();
		
		// Upload the file
		if ( move_uploaded_file($this->tmp_name, $this->directory . $this->filename) ) {
			Debug('UploadFile(), File moved successfully to: "' .
$this->directory . $this->filename . '"');
			// Make sure it is in the right spot
			if ( file_exists($this->directory . $this->filename) ){ 
				// Change the permissions so the file is not locked
				chmod($this->directory . $this->filename, 0775);
				// Return if the file is uploaded successfully
				if (is_writable($this->directory . $this->filename)){
					Debug('UploadFile(), Is Writable! "' . $this->directory .
$this->filename . '"');
					return true;
				}else{
					Debug('UploadFile(), Is Not Writable! "' . $this->directory .
$this->filename . '"');
				}
			}
		}

		// There must have been some issue
		return false;
	}
	

}
?>

Questions:

1. What is the exact procedure to call / use it? 
2. I would also like to add a function to the class which adds certain
items to a MySql db. How can that be done? I know how to do the db bit
I just don't know how to create the function in the class file and
then call it. This is not as important as Q.1
3. I assume that 3 files are involved (1. upload.html which has the
upload form and is posted to file 2 which is upload.php which includes
and calls file 3 upload.class.php). Please can it be organised with
this kind of structure?
4. Finally, after file upload I would like the success or error
message to appear on upload.html not upload.php so some kind of
redirect will be necesary.

Thank you, look forward to hearing from somebody.