PHP分叉和mysql数据库连接问题

我现在正在尝试用php进行分叉。 我想在子进程中进行一些查询和更新。。 问题是，每当一个子进程完成时，它就会关闭连接，从而导致其他查询失败。 下面是我的示例代码

#!/usr/local/bin/php
<?php
set_time_limit(0); # forever program!
$db = mysql_connect("server","user","pwd");
mysql_select_db("schema",$db);
$sql = "query";
$res = mysql_query($sql,$db);
while($rows = mysql_fetch_array($res)) {
  $rv = pcntl_fork();
  if($rv == -1){
    echo "forking failed";
  }
  elseif($rv){
    echo "parent process $rv\n";
    $db = mysql_connect("server","user","pwd",true);
    mysql_select_db("schema",$db);
  }
  else{
    echo "child process $rv\n";
    $sql1 = "another query";
    $res1 = mysql_query($sql1,$db);
    while($messages = mysql_fetch_array($res1)) {
      $sql2 = "update query";
      mysql_query($sql2,$db);
    }
    exit(0);
    //it terminates both child process and mysql connection!
  }
}
?>

#/usr/local/bin/php

尽量不要在父进程中打开另一个SQL连接，并在每个子线程中使用不同的链接标识符变量创建指向MySQL的另一个链接

<?php
  set_time_limit(0); # forever program! 
  $db = mysql_connect("server","user","pwd"); 
  mysql_select_db("schema",$db); 
  $sql = "query"; 
  $res = mysql_query($sql,$db); 
  while($rows = mysql_fetch_array($res)) { 
    $rv = pcntl_fork(); 
    if($rv == -1){ 
      echo "forking failed"; 
    }
    elseif($rv){ 
      echo "parent process $rv\n"; 
      // do nothing with connection here, use old one ($db)
    }
    else
    { 
      $db2 = mysql_connect("server","user","pwd", true); 
      echo "child process $rv\n"; 
      $sql1 = "another query"; 
      $res1 = mysql_query($sql1,$db2); 
      while($messages = mysql_fetch_array($res1)) { 
        $sql2 = "update query"; mysql_query($sql2,$db2); 
      } 
      exit(0); 
    } 
} 
?>