用#hash解释preg_match语法

Question

你能解释一下这个preg_match代码在做什么！ 我也不明白为什么以#tag开头？

if (!preg_match('#\.(.+)$#', $file['name'][$key], $matches)) {..;}

Answer 1

首先，它测试正则表达式 DOESN＆＃39; T MATCH （!preg_match）以下内容：

#\.(.+)$#
---------

Match the character “#” literally «#»
Match the character “.” literally «\.»
Match the regex below and capture its match into backreference number 1 «(.+)»
   Match any single character that is NOT a line break character (line feed) «.+»
      Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Assert position at the end of a line (at the end of the string or before a line break character) (line feed) «$»
Match the character “#” literally «#»

我无法帮助$file['name'][$key]，因为我不知道它是什么，它似乎是filename。