[errorimage.php] Generate error images on the fly in portable PHP

errorimage.php

/**
 * Creates an images containing the specified text.
 * Useful for sending errors back to the client.
 * @package core
 * @param	string	$text			The text to include in the image.
 * @param	int		$target_size	The target width to aim for when creating 
 * 									the image. Not not specified, a value is 
 * 									determined automatically.
 * @return	resource				The handle to the generated GD image.
 */
function errorimage($text, $target_size = null)
{
	$width = 0;
	$height = 0;
	$border_size = 10; // in px, if $target_size isn't null has no effect
	$line_spacing = 2; // in px
	$font_size = 5; // 1 - 5
	
	$font_width = imagefontwidth($font_size);	// in px
	$font_height = imagefontheight($font_size);	// in px
	$text_lines = array_map("trim", explode("\n", $text));
	
	if(!empty($target_size)) {
		$width = $target_size;
		$height = $target_size * (2 / 3);
	}
	else {
		$height = count($text_lines) * $font_height + 
			(count($text_lines) - 1) * $line_spacing +
			$border_size * 2;
		foreach($text_lines as $line)
			$width = max($width, $font_width * mb_strlen($line));
		$width += $border_size * 2;
	}
	
	$image = imagecreatetruecolor($width, $height);
	imagefill($image, 0, 0, imagecolorallocate($image, 250, 249, 251)); // Set the background to #faf8fb
	
	$i = 0;
	foreach($text_lines as $line) {
		imagestring($image, $font_size,
			($width / 2) - (($font_width * mb_strlen($line)) / 2),
			$border_size + $i * ($font_height + $line_spacing),
			$line,
			imagecolorallocate($image, 68, 39, 113) // #442772
		);
		$i++;	
	}
	
	return $image;
}