数据库连接失败SQLSTATE[HY000] [2002] 由于目标计算机积极拒绝，无法连接。<br />
<b>Warning</b>:  Undefined variable $pdo in <b>C:\xampp\htdocs\07201058\index.php</b> on line <b>25</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function prepare() on null in C:\xampp\htdocs\07201058\index.php:12
Stack trace:
#0 C:\xampp\htdocs\07201058\index.php(25): messageAll(NULL)
#1 {main}
  thrown in <b>C:\xampp\htdocs\07201058\index.php</b> on line <b>12</b><br />