Make a (text to image) image a certain width but unlimited length?

Question

I have the code below that makes an image out of a large amount of text. I want that image to be 700px wide. I also want it to keep the paragraph structure that the string has. (the string is from a MySQL database.) How can i achieve that?

                            $font  = 2;
                        $width  = imagefontwidth($font) * strlen($string);
                        $height = imagefontheight($font);

                        $image = imagecreatetruecolor ($width,$height);
                        $white = imagecolorallocate ($image,255,255,255);
                        $black = imagecolorallocate ($image,0,0,0);
                        imagefill($image,0,0,$white);

                        imagestring ($image,$font,0,0,$string,$black);

                ob_start();

                imagepng($image);
                printf('<img src="data:image/png;base64,%s"/>', base64_encode(ob_get_clean()));

                imagedestroy($image);

Secondly, is there a reason why apostrophes aren't showing and I get some weird characters at the start and end of the image?