Code:
<?php
$width = isset($_GET['w']) ? $_GET['w']: '300';
$height = isset($_GET['h']) ? $_GET['h']: '200';
$stroke = isset($_GET['s']) ? $_GET['s']: '222';
$fill = isset($_GET['f']) ? $_GET['f']: 'fafafa';
if (preg_match('([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})', $stroke)) { $stroke = '#'.$stroke; }
if (preg_match('([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})', $fill)) { $fill = '#'.$fill; }
header('Content-Type: image/svg+xml');
?>
<svg xmlns="http://www.w3.org/2000/svg" width="<?php echo $width; ?>" height="<?php echo $height; ?>">
<g>
<rect width="<?php echo $width ?>" height="<?php echo $height; ?>" y="0" x="0" stroke="<?php echo $stroke; ?>" fill="<?php echo $fill; ?>"/>
<line x1="0" x2="100%" y1="0" y2="100%" stroke="<?php echo $stroke; ?>"/>
<line x1="100%" x2="0" y1="0" y2="100%" stroke="<?php echo $stroke; ?>"/>
</g>
</svg>








