mysql转mysqli或pdo

最近在测试一个开源的帮助文档 wiki web help 问题不断，mysql错误提示要求将MySQL链接改为mysqli 或者pdo，按照网上的资料操作几次都失败，想着我大高手如云，求帮忙解决

代码如下：

<?php
$_CONFIG = true;

# obvious db stuff
$CFG_USER = 'root';
$CFG_PASSWORD = '123456';
$CFG_SERVER = 'localhost';
$CFG_DATABASE = 'db';

# this is the return address for emails
$CFG_RETURN_ADDRESS = '';

# for email subject
$CFG_SITE_NAME = '';

# this if true requires registration before edit
$CFG_REGISTERED_ONLY = FALSE;

$con = mysql_connect($CFG_SERVER,$CFG_USER,$CFG_PASSWORD); 
mysql_select_db($CFG_DATABASE, $con);
mysql_set_charset('utf8',$con);

//This stops SQL Injection in POST vars 
foreach ($_POST as $key => $value) { 
    $_POST[$key] = mysql_real_escape_string(str_replace("\\","\\\\",$value)); 
} 

//This stops SQL Injection in GET vars 
foreach ($_GET as $key => $value) { 
    $_GET[$key] = mysql_real_escape_string(htmlspecialchars ($value,ENT_QUOTES,'UTF-8')); 
}
?>

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$coon=mysqli_connct($host,$useranme,$password,$db);
mysqli_query($conn,"set names utf8");

foreach ($_POST as $key => $value) {
$_POST[$key] = mysqli_real_escape_string($conn,str_replace("\","\\",$value));
}
foreach ($_GET as $key => $value) {
$_GET[$key] = mysqli_real_escape_string($conn,htmlspecialchars ($value,ENT_QUOTES,'UTF-8'));
}
下面的同上

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建议直接pdo