这篇文章主要介绍了PHP使用finfo_file()函数检测上传图片类型的实现方法,结合实例形式分析了finfo_file()函数的功能、使用方法及相关注意事项,需要的朋友可以参考下
本文实例讲述了PHP使用finfo_file()函数检测上传图片类型的实现方法。分享给大家供大家参考，具体如下：
在输入输出中，文件的交互必不可少，比如文件的上传什么的。这里我们来解决一个小问题，就是如何判断用户上传文件的文件类型。
举一个应用场面：在我们的Web应用中，比如用户上传头像，要求是png,jpg,gif格式，接收到图片后会根据图片格式类型做不同的头像切割处理，但个别用户会传一些只更改过文件后缀的非标准图片，比如nowamagic.jpg 强行修改成 nowamagic.png，这样程序无法对该类型图片进行切割，切割失败。这个时候就需要对文件进行检测，并且仅仅根据后缀来判断是不行的。
这种这么常见的需求，PHP肯定自带了某些函数来实现的，这个函数就是 finfo_file。
finfo_file
(PHP >= 5.3.0, PECL fileinfo >= 0.1.0)
finfo_file -- finfo::file — Return information about a file，This function is used to get information about a file.
函数很简单，看看官方文档就大概清楚了，这里就举一个使用例子吧，就是上传一张图片，并判断它的类型：
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<head>
<title>文件上传</title>
</head>
<body>
<form accept="" method="post" enctype="multipart/form-data">
<input type="file" name="img[]" /><br />
<input type="submit" name="s" /><br />
</form>
<?php
//上传文件信息
$img = $_FILES['img'];
if ($img)
{
//文件存放目录，和本php文件同级
$dir = dirname(file);
$filename = $img['name'][0];
$tempname = $img['tmp_name'][0];
$savepath = "$dir\\$filename";
$state = move_uploaded_file($tempname, $savepath);
//如果上传成功，预览
if($state)
{
echo "<img src='$filename' alt='$filename' /> ";
}
$finfo = finfo_open(FILEINFO_MIME_TYPE);
//$mime = finfo_file($finfo, dirname(FILE)."/".$filename);
$mime = finfo_file($finfo, $savepath);
echo $mime;
}
?>
</body>
</html>需要注意的是，finfo_file 函数需要 PHP 版本 >= 5.3.0，如果低于 5.3，那么需要到 php.ini 里，将 extension=php_fileinfo.dll 前面的分号去掉来启用。
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