PHP判断上传文件类型

PHP判断上传文件类型，很实用的，可以判断.csv格式

<?php
$allowedExtensions = array("txt","csv","htm","html","xml",
    "css","doc","xls","rtf","ppt","pdf","swf","flv","avi",
    "wmv","mov","jpg","jpeg","gif","png"); 
    foreach ($_FILES as $file) {
    if ($file['tmp_name'] > '') {
      if (!in_array(end(explode(".",
            strtolower($file['name']))),
            $allowedExtensions)) {
       die($file['name'].' is an invalid file type!<br/>'.
        '<a href="javascript:history.go(-1);">'.
        '<&lt Go Back</a>');
      }
}
}
?>