How to get the file extension in php, _PHP tutorial-PHP Tutorial-php.cn

How to get the file extension in php, _PHP tutorial

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Release： 2016-07-12 08:51:02

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How to get the suffix of a file in php,

such as the suffix of an image file, jpg or gif, etc.

There are two methods

1. If $img is the image file name

$img=12345.gif;
$img_ext = substr($img, strrpos($img, '.'));

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Second, use php array, first read the file name string into the array

$ext2=explode(".",$img);
      $count=count($ext2);
      $count2=$count-1;
      $file_name  = $urlstr .'.'.$ext2[$count2];//得到后缀并重新定义新的文件名$file_name

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Also attached are the methods summarized by other friends:

第1种方法：
function get_extension($file)
{
substr(strrchr($file, '.'), 1);
}
第2种方法：
function get_extension($file)
{
return substr($file, strrpos($file, '.')+1);
}
第3种方法：
function get_extension($file)
{
return end(explode('.', $file));
}
第4种方法：
function get_extension($file)
{
$info = pathinfo($file);
return $info['extension'];
}
第5种方法：
function get_extension($file)
{
return pathinfo($file, PATHINFO_EXTENSION);
}

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After a quick look at the above methods, they all seem to work, especially methods 1 and 2, which I have been using before I didn’t know that pathinfo has a second parameter. But if you think about it carefully, the first four methods have various shortcomings. To obtain the file extension completely correctly, you must be able to handle the following three special situations.

No file extension
The path contains characters., such as /home/test.d/test.txt
The path contains the character ., but the file has no extension. Such as /home/test.d/test

Obviously: 1 and 2 cannot handle the third situation, and 3 cannot handle the first and third situations correctly. 4 is handled correctly, but when the extension is not present, a warning is issued. Only method 5 is the most correct method. By the way, take a look at the pathinfo method. The introduction on the official website is as follows:

$file_path = pathinfo('/www/htdocs/your_image.jpg');
 
echo "$file_path ['dirname']\n";
echo "$file_path ['basename']\n";
echo "$file_path ['extension']\n";
echo "$file_path ['filename']\n"; // only in PHP 5.2+

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It will return an array containing up to four elements, but there will not always be four. For example, if there is no extension, there will be no extension element, so the warning will be found in the fourth method. . But phpinfo also supports the second parameter. You can pass a constant to specify a certain part of the data to be returned:

PATHINFO_DIRNAME - 目录
PATHINFO_BASENAME - 文件名（含扩展名）
PATHINFO_EXTENSION - 扩展名
PATHINFO_FILENAME - 文件名（不含扩展名，PHP>5.2）

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The values of these four constants are 1, 2, 4, and 8. At first, I thought I could specify multiple ones through the OR operation:
pathinfo($file, PATHINFO_EXTENSION | PATHINFO_FILENAME);
Later I found out that this doesn't work, it will only return the smallest of several OR constants. That is, the smallest bit among the four flag bits is a constant of 1.