我个人将每次出现*或\的过程都用一个计数器循环，然后根据该字符用相应的HTML标记替换计数(例如，如果计数为偶数并且您打了星号，则将其替换为<em>，如果它是奇数，则将其替换为</em>，依此类推.)

Personally, I'd loop through each occurrence of * or \ with a counter, and replace the character with the appropriate HTML tag based on the count (for example, if the count is even and you hit an asterisk, replace it with <em>, if it's odd then replace it with </em>, etc).

但是，如果您确定只需要支持几种简单的标记，则针对每种标记的正则表达式可能是最简单的解决方案.像这样的星号，例如(未经测试):

But if you're sure that you only need to support a couple simple kinds of markup, then a regular expression for each might be the easiest solution. Something like this for asterisks, for example (untested):

preg_replace('/\*([^*]+)\*/', '<em>\\1</em>', $text);

反斜杠也类似.