如何獲取（提取）PHP文件擴展名？ - How do I get (extract) a file extension in PHP?

問題：

This is a question you can read everywhere on the web with various answers: 這是一個您能夠在網上處處閱讀的各類問題，並有各類答案：

$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，總有「最佳方法」，它應該在堆棧溢出中。

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解決方案：

參考一： https://stackoom.com/question/jEK/如何獲取-提取-PHP文件擴展名
參考二： https://oldbug.net/q/jEK/How-do-I-get-extract-a-file-extension-in-PHP