Programming PHP, 2nd Edition

Dynamically Generated Buttons

A popular use for dynamically generated images is to create images for buttons on the fly (this was introduced to you in Chapter 1 as well). Normally, a blank button background image is used and text is overlaid on top of it, as shown in Example 9-8.

Example 9-8. Creating a dynamic button

<?php
 $font = 'times';
 if (!$size) $size = 12;
 $im = ImageCreateFromPNG('button.png');
 // calculate position of text
 $tsize = ImageTTFBBox($size,0,$font,$text);
 $dx = abs($tsize[2]-$tsize[0]);
 $dy = abs($tsize[5]-$tsize[3]);
 $x = ( ImageSx($im) - $dx ) / 2;
 $y = ( ImageSy($im) - $dy ) / 2 + $dy;
 // draw text
 $black = ImageColorAllocate($im,0,0,0);
 ImageTTFText($im, $size, 0, $x, $y, $black, $font, $text);
 header('Content-Type: image/png');
 ImagePNG($im);
?>

In this case, the blank button (button.png) looks as shown in Figure 9-7.

Figure 9-7. Blank Button

The script in Example 9-8 can be called from a page like this:

<img src="button.php?text=PHP+Button">

This HTML generates the button shown in Figure 9-8.

Figure 9-8. Button with generated text label

The + character in the URL is the encoded form of a space. Spaces are illegal in URLs and must be encoded. Use PHP’s urlencode( ) function to encode your button strings. For example:

<img src="button.php?text=<?php echo urlencode('PHP ...