要检查是否有上传的文件，您需要检查文件的大小。
然后检查它是否是一个图像，你需要使用getimagesize（）函数。请看下面我的脚本：
于飞：

<form action="index.php?act=s" method="post" enctype="multipart/form-data">
<input type="file" name="image" value=""/>
<input type="submit">
</form>

PHP程式码：

<?php  
if(isset($_GET['act'])){
    // Check if there is a file uploaded
    if($_FILES["image"]["size"]>0){
        echo "There is a file uploaded<br>";
        // Check if its an image
            $check_if_image = getimagesize($_FILES["image"]["tmp_name"]);
            if($check_if_image !== false) {
                echo "Image = " . $check_if_image["mime"] . ".";            
            } else {
                echo "Not an image";            
            }
    }
    else{
        echo "There is NO file uploaded<br>";
    }   
}   
?>