The examples in function imagettfbbox() gave me many problems because of misunderstand of how the text is positionned in the box.

So I did a new example:
- writing a text
- in the correct position in its box
- with a padding around

Enjoy !
Mike

<?

// some settings
    $angle = 0;
    $text = 'Ühg 0123456789';
    $font_face = dirname(__FILE__).'/verdana.ttf'; // put the file in the same directory
    $font_size = 9; //(int) pixels in GD 1, or points in GD 2

// retrieves box frame
    $box = imagettfbbox($font_size, 0, $font_face, $text);
    $bottom_left_x = $box[0]; // used below
    $bottom_left_y = $box[1]; // used below
    $bottom_right_x = $box[2]; // used below
    $bottom_right_y = $box[3];
    $top_right_x = $box[4];
    $top_right_y = $box[5];
    $top_left_x = $box[6];
    $top_left_y = $box[7]; // used below

// define width and height of the text box
    $box_w = abs($bottom_left_x) + abs($bottom_right_x);
    $box_h = abs($bottom_left_y) + abs($top_left_y);

// add padding
    $padding_x = 5;
    $padding_y = 5;
    $box_w = $box_w + 2 * $padding_x;
    $box_h = $box_h + 2 * $padding_y;

// origin of the text = baseline of the first char
    $text_x = abs($bottom_left_x) -1 + $padding_x;
    $text_y = $box_h -1 - abs($bottom_left_y) - $padding_y;
    
// mysterious correction for the characters going low like pgjq
    if(abs($bottom_left_y) <= 1) $box_h--;

// create the image
    $img = imagecreatetruecolor($box_w, $box_h);
 
// define some colors
    $white = imagecolorallocate($img,255,255,255);
    $black = imagecolorallocate($img,0,0,0);
    $lightgrey = imagecolorallocate($img, 200, 200, 200);
    $grey = imagecolorallocate($img,100,100,100);
    $yellow = imagecolorallocate($img, 0xFF, 0xFF, 0x00);
 
// attribute colors
    $font_color =  $black;
    $padding_color =  $lightgrey;
    $background_color =  $yellow;
 
// fill image with background color
    imagefill($img, 0, 0, $background_color);

// fill image with padding color
    imagefilledrectangle($img, 0, 0, $box_w, $padding_y - 1, $padding_color); // top
    imagefilledrectangle($img, 0, 0, $padding_x - 1, $box_h - 1, $padding_color); // left
    imagefilledrectangle($img, 0, $box_h - $padding_y -1, $box_w, $box_h - 1, $padding_color); // bottom
    imagefilledrectangle($img, $box_w - $padding_x, 0, $box_w - 1, $box_h - 1, $padding_color); // right

//write text
imagettftext($img, $font_size, 0, $text_x, $text_y, $font_color, $font_face, $text);

//rotate image
    if ($angle > 0) $img = imagerotate($img, $angle, $white);

// send header
    header("Content-type: image/gif");
 
//sends image
    imagegif($img);
    imagedestroy($img);
?>