How Can You Extract the True File Extension from a Filename?

Determining the True File Extension

Many developers encounter the need to extract the file extension from a filename. While it's common to employ solutions that simply parse the filename string and cut off anything following a period (.), this approach can lead to inaccurate results, especially if the filename contains multiple extensions.

For instance, the following scripts may fail to remove extensions properly:

• /.[^.] $/
• substr($filename, 0, (strlen ($filename)) - (strlen (strrchr($filename,'.'))))

Both of these scripts rely on a delimiter ('.') to isolate the extension. However, if the filename includes a string like "This.is example of somestring," they will only remove the first period and yield "This" instead of the desired result, "somestring."

Using pathinfo() for Accurate Extension Removal

To avoid such irregularities, it's recommended to leverage the pathinfo() function provided by PHP. This function offers a robust method for obtaining various information about a file path, including its filename and extension.

Consider the following example:

$filename = pathinfo('filename.md.txt', PATHINFO_FILENAME); // returns 'filename.md'

By specifying PATHINFO_FILENAME as the second parameter, pathinfo() isolates the filename portion of the given path, including any extensions. As demonstrated above, if the filename contains multiple extensions, pathinfo() will correctly extract the true extension.

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