$cookie = "csrftoken=P7UBtv3lTNktgrqQglECF7Wj3MWUNJc1; qwqwqwxsewwewe123434dsw4e4d23 qw2323ss";

    preg_match('/csrftoken=(.*?);/', $cookie, $matches);//获取匹配的字符串  参数1，规则，2；获取的字符串 3，获得结果集

    $csrftoken = $matches[1];

            var_dump($matches);
            得到:     
[  0 => "csrftoken=P7UBtv3lTNktgrqQglECF7Wj3MWUNJc1;"  1=>"P7UBtv3lTNktgrqQglECF7Wj3MWUNJc1"]