PHP生成縮略圖

/**
 * 生成唯一字符串
 * @return string
 */
function getUniName(){
	return md5(uniqid(microtime(true),true));
}

/**
 * 得到文件的擴展名
 * @param string $filename
 * @return string
 */
function getExt($filename){
	return strtolower(end(explode(".",$filename)));
}

/**
 * 生成縮略圖
 * @param string $filename
 * @param string $destination
 * @param int $dst_w
 * @param int $dst_h
 * @param bool $isReservedSource
 * @param number $scale
 * @return string
 */
function thumb($filename,$destination=null,$dst_w=null,$dst_h=null,$isReservedSource=true,$scale=0.5){
	//默認不保留源文件$isReservedSource=false
	list($src_w,$src_h,$imagetype)=getimagesize($filename);
	if(is_null($dst_w)||is_null($dst_h)){
		$dst_w=ceil($src_w*$scale);
		$dst_h=ceil($src_h*$scale);
	}
	$mime=image_type_to_mime_type($imagetype);
	//echo $mime;//image/jpeg,image/gif
	$createFun=str_replace("/", "createfrom", $mime);//imagecreatefromjpeg
	$outFun=str_replace("/", null, $mime);//imagejpeg
	$src_image=$createFun($filename);
	$dst_image=imagecreatetruecolor($dst_w, $dst_h);
	imagecopyresampled($dst_image, $src_image, 0,0,0,0, $dst_w, $dst_h, $src_w, $src_h);
	if($destination&&!file_exists(dirname($destination))){
		mkdir(dirname($destination),0777,true);
	}
	$dstFilename=$destination==null?getUniName().".".getExt($filename):$destination;
	$outFun($dst_image,$dstFilename);
	imagedestroy($src_image);//銷燬資源
	imagedestroy($dst_image);//銷燬資源
	if(!$isReservedSource){
		unlink($filename);//刪掉源文件
	}
	return $dstFilename;
}