PHP file extension to determine and obtain file name extension of the N-way _php instance

The following code is the php file name extension judgment

<! doctype>
 
 

n ways to get file name extensions in PHP

Basically, in the following ways:

The 1th method:

function Get_extension ($file)
{
substr (STRRCHR ($file, '. '), 1);
}

The 2nd method:

function Get_extension ($file)
{return
substr ($file, Strrpos ($file, '. ') +1);
}

The 3rd method:

function Get_extension ($file)
{return end
(Explode ('. ', $file));
}

The 4th method:

function Get_extension ($file)
{
$info = PathInfo ($file);
return $info [' extension '];
}

The 5th method:

function Get_extension ($file)
{return
pathinfo ($file, pathinfo_extension);
}

The above several ways coarse look, seems to be all right, especially 1, 2 kinds of methods, before I do not know PathInfo has the second parameter has been used. But think about it, the first four methods have all kinds of problems. To get the file extensions exactly right, you must be able to handle the following three special cases.

No file name extension

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

The path contains characters., but the file does not have an extension. such as/home/test.d/test

Obviously: 1, 2 can not deal with the third situation, 3 can not correctly deal with the 13th case. 4 can be handled correctly, but a warning is issued when no extension exists. Only the 5th method is the right approach. By the way, look at the PathInfo method. The official website introduces 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 returns an array containing up to four elements, but does not always have four, for example, without an extension, there will be no extension element, so the 4th method will find the warning. But Phpinfo also supports the second parameter. You can pass a constant that specifies the data to return a part of:

Pathinfo_dirname-Table of Contents
Pathinfo_basename-file name (including extension)
Pathinfo_extension-name extension
Pathinfo_filename-filename (without extension, php>5.2)

The values for these four constants are 1, 2, 4, 8, and at first I thought you could specify multiple by or operation:

PathInfo ($file, Pathinfo_extension | Pathinfo_filename);

It turns out that this is not going to work, and that only returns a few of the ones that are the smallest of the constants or operands. That is, a constant with a minimum of 1 digits in four flags.

The above content for you to introduce the PHP file extension to determine the name and get the file name extension of the n methods, I hope you like.