PHP picture background filling example

/**
* Add background
* @param string $src Image path
* @param int $w Background image width
* @param int $h Background image height
* @return Return the image with background
* **/
public function addBg($src,$w,$h)
{
$bg = imagecreatetruecolor($w,$h );
$white = imagecolorallocate($bg,255,255,255);
imagefill($bg,0,0,$white);//Fill the background
//Get the target image information
$ info=getimagesize($src);
$width=$info[0];//Target image width
$height=$info[1];//Target image height
switch ($info[2]){
case 1:
 $img = imagecreatefromgif($src);
 break;
 case 2:
 $img = imagecreatefromjpeg($src);
 break;
 case 3:
 $img = imagecreatefrompng($src);
 break;
 default:
 exit('Unsupported image format');
 break;
}
if($height < $h)
{
$x=0;
$y=($h-$height)/2 ;//Vertical centering
}
if($width < $w)
{
$x=($w-$width)/2;//Horizontal centering
$y=0;
}
if($height < $h && $width < $w){
$x = ($w-$width)/2;
$y = ($h-$height)/2;
}
imagecopymerge($bg,$ img,$x,$y,0,0,$width,$height,100);
imagejpeg($bg,$src,100);
imagedestroy($bg);
imagedestroy($img);
return $ src;
}