regex:匹配段落内的内容

/^A:([a-z]*)(?:(?!(?:\r?\n){2,}).)*^C:([a-z]*)/sm

m

/A:([a-z]*)\v*.*\v?C:([a-z]*)\v*/m

\v

$str=<<<A
A:one
C:foo

A:two
B:rofl, some rubbish :::

A:three
B:lol
C:bar
A;

$s = explode("\n\n",$str);
foreach($s as $k){
    if(strpos($k,"A:") !==FALSE && strpos($k,"C:") !==FALSE){
        $a = array_filter ( ( preg_split("/([A-Z]):|\n+/sm",$k) ) );
        print_r($a);
    }
}

$ php test.php
Array
(
    [1] => one
    [3] => foo
)
Array
(
    [1] => three
    [3] => lol
    [5] => bar
)