下面的代码演示了php中如何获取用户上传的文件，并限制文件类型的一般图片文件，最后保存到服务器

<?php  $allowedExts = array("gif", "jpeg", "jpg", "png");  $extension = end(explode(".", $_FILES["file"]["name"]));  if ((($_FILES["file"]["type"] == "image/gif")  || ($_FILES["file"]["type"] == "image/jpeg")  || ($_FILES["file"]["type"] == "image/jpg")  || ($_FILES["file"]["type"] == "image/pjpeg")  || ($_FILES["file"]["type"] == "image/x-png")  || ($_FILES["file"]["type"] == "image/png"))  && ($_FILES["file"]["size"] < 20000)  && in_array($extension, $allowedExts))    {    if ($_FILES["file"]["error"] > 0)      {      echo "Return Code: " . $_FILES["file"]["error"] . "<br>";      }    else      {      echo "Upload: " . $_FILES["file"]["name"] . "<br>";      echo "Type: " . $_FILES["file"]["type"] . "<br>";      echo "Size: " . ($_FILES["file"]["size"] / 1024) . " kB<br>";      echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br>";         if (file_exists("upload/" . $_FILES["file"]["name"]))        {        echo $_FILES["file"]["name"] . " already exists. ";        }      else        {        move_uploaded_file($_FILES["file"]["tmp_name"],        "upload/" . $_FILES["file"]["name"]);        echo "Stored in: " . "upload/" . $_FILES["file"]["name"];        }      }    }  else    {    echo "Invalid file";    }  ?>