PHP使用mysql与mysqli连接Mysql数据库用法示例

<?php
  /**
  * @Author:   HTL
  * @Description: Description
  */
  // 降低PHP默认的错误级别
  // 只显示除禁用以外的所有错误
  // 解决因为PHP5.3+版本太高而导致在使用mysql_connect时出现的弃用警告“Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead”
  error_reporting(E_ALL ^ E_DEPRECATED);
  $db_host="localhost";
  $db_user="root";
  $db_passwd="";
  $db_name="mysql";
  echo("<BR>---------------------------mysql_connect------------------------<BR><BR>");
  $query = "SELECT SESSION_USER(), CURRENT_USER(),now();";
  $conn = mysql_connect($db_host, $db_user,$db_passwd);
  if (!$conn)
  {
   die('Could not connect: ' . mysql_error());
  }
  mysql_select_db($db_name, $conn);
  $result = mysql_query($query);
  while($row = mysql_fetch_array($result)){
   var_dump($row);
  }
  mysql_close($conn);
  echo("<BR>---------------------------mysqli_connect------------------------<BR><BR>");
  $conn = mysqli_connect($db_host, $db_user, $db_passwd,$db_name) ;
  if (!$conn)
  {
   die('Could not connect: ' . mysqli_error());
  }
  //execute the query.
  $result = mysqli_query($conn, $query);
  //display information:
  while($row = mysqli_fetch_array($result)) {
    var_dump($row);
  }
  mysqli_close($conn);
  exit();
?>