如何获取（提取）PHP文件扩展名？ - How do I get (extract) a file extension in PHP?

问题：

This is a question you can read everywhere on the web with various answers: 这是一个您能够在网上处处阅读的各类问题，并有各类答案：

$ext = end(explode('.', $filename));
$ext = substr(strrchr($filename, '.'), 1);
$ext = substr($filename, strrpos($filename, '.') + 1);
$ext = preg_replace('/^.*\.([^.]+)$/D', '$1', $filename);

$exts = split("[/\\.]", $filename);
$n    = count($exts)-1;
$ext  = $exts[$n];

etc. 等等

However, there is always "the best way" and it should be on Stack Overflow. 可是，总有“最佳方法”，它应该在堆栈溢出中。

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解决方案：

参考一： https://stackoom.com/question/jEK/如何获取-提取-PHP文件扩展名
参考二： https://oldbug.net/q/jEK/How-do-I-get-extract-a-file-extension-in-PHP