How to implement common file upload classes using PHP

<?php
/** * 上传文件类 * @param _path : 服务器文件存放路径 * @param _allowType : 允许上传的文件类型和所对应的MIME * @param _file : 上传的文件信息*/
    class Upload {
    private $_path;
    private $_allowType;
    private $_file;
    /** * 构造函数 * @param string : 服务器上存放上传文件的路径*/
    function __construct( $path = &#39;&#39; ) {
    $this->_path = $path;
    $this->_allowType = array( // images &#39;bmp&#39; => &#39;image/x-ms-bmp&#39;, &#39;jpg&#39; => &#39;image/jpeg&#39;, &#39;jpeg&#39; => &#39;image/jpeg&#39;, &#39;gif&#39; => &#39;image/gif&#39;, &#39;png&#39; => &#39;image/png&#39;, &#39;tif&#39; => &#39;image/tiff&#39;, &#39;tiff&#39; => &#39;image/tiff&#39;, &#39;tga&#39; => &#39;image/x-targa&#39;, &#39;psd&#39; => &#39;image/vnd.adobe.photoshop&#39;, //文本 &#39;txt&#39; => &#39;text/plain&#39;, &#39;php&#39; => &#39;text/x-php&#39;, &#39;html&#39; => &#39;text/html&#39;, &#39;htm&#39; => &#39;text/html&#39;, &#39;js&#39; => &#39;text/javascript&#39;, &#39;css&#39; => &#39;text/css&#39;, &#39;rtf&#39; => &#39;text/rtf&#39;, &#39;rtfd&#39; => &#39;text/rtfd&#39;, &#39;py&#39; => &#39;text/x-python&#39;, &#39;java&#39; => &#39;text/x-java-source&#39;, &#39;rb&#39; => &#39;text/x-ruby&#39;, &#39;sh&#39; => &#39;text/x-shellscript&#39;, &#39;pl&#39; => &#39;text/x-perl&#39;, &#39;sql&#39; => &#39;text/x-sql&#39;, //应用 &#39;exe&#39; => &#39;application/octet-stream&#39;, &#39;doc&#39; => &#39;application/vnd.ms-word&#39;, &#39;docx&#39; => &#39;application/vnd.ms-word&#39;, &#39;xls&#39; => &#39;application/vnd.ms-excel&#39;, &#39;ppt&#39; => &#39;application/vnd.ms-powerpoint&#39;, &#39;pps&#39; => &#39;application/vnd.ms-powerpoint&#39;, &#39;pdf&#39; => &#39;application/pdf&#39;, &#39;xml&#39; => &#39;application/xml&#39;, //音频 &#39;mp3&#39; => &#39;audio/mpeg&#39;, &#39;mid&#39; => &#39;audio/midi&#39;, &#39;ogg&#39; => &#39;audio/ogg&#39;, &#39;mp4a&#39; => &#39;audio/mp4&#39;, &#39;wav&#39; => &#39;audio/wav&#39;, &#39;wma&#39; => &#39;audio/x-ms-wma&#39;, //视频 &#39;avi&#39; => &#39;video/x-msvideo&#39;, &#39;dv&#39; => &#39;video/x-dv&#39;, &#39;mp4&#39; => &#39;video/mp4&#39;, &#39;mpeg&#39; => &#39;video/mpeg&#39;, &#39;mpg&#39; => &#39;video/mpeg&#39;, &#39;mov&#39; => &#39;video/quicktime&#39;, &#39;wm&#39; => &#39;video/x-ms-wmv&#39;, &#39;flv&#39; => &#39;video/x-flv&#39;, &#39;mkv&#39; => &#39;video/x-matroska&#39; );
}
/** * 上传函数 * @param string : 表单元素的name 值 * @return [type]*/
    public function upload( $txtName = &#39;&#39; ) {
    $this->_file = $_FILES[$txtName];
    if( $this->_file[&#39;error&#39;] == 0) {
    $fileType = end( explode(&#39;.&#39;, $this->_file[&#39;name&#39;] ));
    $allowType = array();
    foreach( $this->_allowType as $item=>$value ) {
    $allowType[] = $item;
}
if( !in_array($fileType, $allowType)) {
    die(&#39;上传的文件格式不正确！&#39;);
}
else {
    if(move_uploaded_file($this->file[&#39;tmp_name&#39;], ($this->path).$this->file[&#39;name&#39;])) {
    echo "<script>alert(&#39;上传成功!&#39;)</script>";
}
else {
    echo "<script>alert(&#39;上传失败!&#39;);
    </script>";
}
}
}
else {
    //没有正确上传 switch ($this->file[&#39;error&#39;]) {
    case 1: die(&#39;文件大小超过系统限制。&#39;);
    break;
    case 2: die(&#39;文件大小超过预定义限制。&#39;);
    break;
    case 3: die(&#39;文件为完全上传。&#39;);
    break;
    case 4: die(&#39;未上传任何文件。&#39;);
    break;
    default: die(&#39;上传出错&#39;);
    break;
}
} }
//end upload
}