用php生成上传图片的缩略图问题

请看代码：

list($maintype,$subtype)=explode("/", $_FILES['upload']['type']);
		function set_thumb ($width, $height) {      
			$thumb_width  = $width;      
        	$thumb_height = $height;      
    	} 
    	//创建缩略图,以相同的扩展名生成缩略图      
    	//$src_file : 来源图像路径 , $thumb_file : 缩略图路径      
    	function create_thumb ($src_file,$thumb_file) {      
       		 $t_width  = $thumb_width;      
        	 $t_height = $thumb_height;      
        	if (!file_exists($src_file)) return false;      
        	$src_info = getImageSize($src_file);      
        	//如果来源图像小于或等于缩略图则拷贝源图像作为缩略图,免去操作      
        	if ($src_info[0] <= $t_width && $src_info[1] <= $t_height) {      
            	if (!copy($src_file,$thumb_file)) {      
               	 	return false;      
            	}      
            	return true;      
        	}            
        	//按比例计算缩略图大小      
        	if (($src_info[0]-$t_width) > ($src_info[1]-$t_height)) {      
            	$t_height = ($t_width / $src_info[0]) * $src_info[1];      
       	 	} else {      
            	$t_width = ($t_height / $src_info[1]) * $src_info[0];      
        	}      
         
        	switch ($subtype) {      
            	case 'jpg' :      
                	$src_img = ImageCreateFromJPEG($src_file); break;      
            	case 'png' :      
                	$src_img = ImageCreateFromPNG($src_file); break;      
            	case 'gif' :      
                	$src_img = ImageCreateFromGIF($src_file); break;      
        	}      
        	//创建一个真彩色的缩略图像      
        	$thumb_img = @ImageCreateTrueColor($t_width,$t_height);      
        	//ImageCopyResampled函数拷贝的图像平滑度较好，优先考虑      
        	if (function_exists('imagecopyresampled')) {      
            	@ImageCopyResampled($thumb_img,$src_img,0,0,0,0,$t_width,$t_height,$src_info[0],$src_info[1]);      
        	} else {      
            	@ImageCopyResized($thumb_img,$src_img,0,0,0,0,$t_width,$t_height,$src_info[0],$src_info[1]);      
        	}      
        	//生成缩略图      
        	switch ($subtype) {      
            	case 'jpg' :      
                	ImageJPEG($thumb_img,$thumb_file); break;      
            	case 'gif' :      
               	 	ImageGIF($thumb_img,$thumb_file); break;      
            	case 'png' :      
                	ImagePNG($thumb_img,$thumb_file); break;      
        	}      
        	//销毁临时图像      
			@ImageDestroy($src_img);      
        	@ImageDestroy($thumb_img);
        	return true;      
    	}

我是这么调用的：

$upfile='uploads/'.rand(0,10000).date('YmdHis').iconv("utf8", "UTF-8", $_FILES['upload']['name']);
		$thumb_file='uploads/'.'thumb_'.rand(0,10000).date('YmdHis').iconv("utf8", "UTF-8", $_FILES['upload']['name']);
        if(is_uploaded_file($_FILES['upload']['tmp_name'])){
			
			if(!move_uploaded_file($_FILES['upload']['tmp_name'], $upfile)){
				echo "<script language='javascript'>";
				echo "alert('不能移动到指定目录！');";
				echo "window.history.go(-1);";
				echo "</script>";
				exit();
			}
			@unlink($_FILES['upload']['tmp_name']);
			set_thumb(100,80);
			if(create_thumb($upfile,$thumb_file)){
				$thumbfile=$thumb_file;
			} 
        ...//中间省略一些数据库操作代码

数据库里有缩略图的路径，但文件夹里面没有生成缩略图

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imagick不解释

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谢谢大家的回答 我后来检查了一遍代码发现是iconv("utf8", "UTF-8", $_FILES['upload']['name'])这句代码惹的祸，它直接把图片的后缀名给去掉了，所以导致后面的create_thumb()函数不能成功生成缩略图，再次感谢大家的帮助。