Summary of N methods to obtain file extension in PHP

Summary of N methods to obtain file extension in PHP_PHP tutorial

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Release： 2016-07-21 15:20:22

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Method 1:

Copy code The code is as follows:

 
function get_extension($file) 
{ 
 substr(strrchr($file, '.'), 1); 
} 

The second method:

Copy code The code is as follows:

 
function get_extension($file) 
{ 
return substr($file, strrpos($file, '.')+1); 
 } 

The third method:

Copy code The code is as follows:

 
function get_extension( $file) 
{ 
return end(explode('.', $file)); 
} 

The 4th method:

Copy code The code is as follows:

 
function get_extension($file) 
{ 
$info = pathinfo($file); 
return $info['extension']; 
} 

The fifth method:

Copy code The code is as follows:

 
function get_extension($file) 
{ 
return pathinfo($file, PATHINFO_EXTENSION); 
} 

A rough look at the above methods After a while, everything seems 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 the characters ., such as /home/test.d/test.txt
The path contains the characters ., but the file has no extension. For example, /home/test.d/test
It 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 Returns 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 fourth method will detect a warning. 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 - directory
PATHINFO_BASENAME - file name (including extension)
PATHINFO_EXTENSION - extension
PATHINFO_FILENAME - file name (without extension, PHP>5.2)
The values of these four constants are 1, 2, 4, and 8 respectively. 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.
The following are some supplementary methods
1. PHP explode function

Copy the code The code is as follows:

 
$pic = 'abc.php'; 
$pics = explode('.' , $pic); 
echo $num = count($pics); 
echo '

In this way,
.php can be output.

The following uses foreach

Copy the code The code is as follows:

 
foreach ($pics as $value) / /2 
{ 
$a = $value; 
} 
echo $a.'
'; 

It would be better to have one I recommend using this function end function shortcut end function usage

Copy code The code is as follows:

 
echo end($pics) ; 
echo '
'; 

Other access methods can be determined when the file is uploaded, but that requires the file to be uploaded and we cannot use $_FILES to operate.