<?php
class Graph {
        var $format='gif';
        var $error = '';
        var $image = '';
        var $filename = '';

        function image($filename='') {
                $this->error = '';
                if (empty($this->image)) { $this->image = $this->createImage(); }
                if (!empty($filename)) {
                        switch ($this->format) {
                                case 'gif':
                                        imageGif($this->image,$filename);
                                        break;
                                case 'jpeg':
                                        imageJpeg($this->image,$filename);
                                        break;
                                case 'png':
                                        imagePng($this->image,$filename);
                                        break;
                        }
                }
                return $this->image;
        }

        function setFormat($format='gif') {
                $this->error = '';
                if (preg_match('/gif|jpeg|png/',$format)) {
                        $this->format = $format;
                }
                else {
                        $this->error = 'Invalid image format. Use gif,jpeg or png instead.';
                }
        }

        function printHTML() {
                $this->error = '';
                if (empty($this->image)) { $this->image = $this->createImage(); }
                Header('Content-type: image/'.$this->format);
                switch ($this->format) {
                        case 'gif':
                                imageGif($this->image);
                                break;
                        case 'jpeg':
                                imageJpeg($this->image);
                                break;
                        case 'png':
                                imagePng($this->image);
                                break;
                }
        }

        function createImage() {
                $im = '';
                return $im;
        }

        function error() {
                return $this->error;
        }
}
?>