How to get file extension in php

This article summarizes several ways to use PHP to obtain the suffix name of a file. It is very simple and practical. Friends in need can refer to it

For example, the suffix of image files, jpg or gif, etc.

There are two methods

First, if $img is the image file name

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

Second, use the 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

In addition, attach the method 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);
}

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.

1. No file extension

2. The path contains the characters ., such as /home/test.d/test.txt

3. The path contains the character ., but the file has no extension. For example, /home/test.d/test
   

is obvious: 1 and 2 cannot handle the third situation, and 3 cannot correctly handle the first and third situations. 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+

It will return an array containing up to four elements, but there will not always be four, such as in 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）

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

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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