替换字符串PHP中多次出现的单词

Question

我只想替换以下字符串：

This is my first sentence.
.:.
This is my second sentence.
.:.
This is my third sentence.
.:.

输出应该是：

This is my first sentence.
1
This is my second sentence.
2
This is my third sentence.
3

我怎样才能更有效，更轻松地完成这项工作？

Answer 1

echo preg_replace_callback("/@/",
    function(){static $count=0; return ++$count;},
    "A@B@C@");