替换字符串PHP词多次出现

Question

我只是想替换以下字符串：

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

输出应该是这样的：

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

我怎么能做到这一点的更有效，更容易办法？

Answer 1

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