php SQL Injection with MySQL

The used SELECT statements have a different number of columns

CREATE TABLE `article` (
`articleid` int(11) NOT NULL auto_increment,
`title` varchar(100) NOT NULL default '',
`content` text NOT NULL,
PRIMARY KEY (`articleid`)
) TYPE=MyISAM AUTO_INCREMENT=3 ;

#
# 导出表中的数据 `article`
#

INSERT INTO `article` VALUES (1, '我是一个不爱读书的孩子', '中国的教育制度真是他妈的落后！如果我当教育部长。我要把所有老师都解雇！');
INSERT INTO `article` VALUES (2, '我恨死你', '我恨死你了，你是什么东西啊');

<?php
$servername = "localhost";
$dbusername = "root";
$dbpassword = "";
$dbname = "injection";

mysql_connect($servername,$dbusername,$dbpassword) or die ("数据库连接失败");

$sql = "SELECT * FROM article WHERE articleid='$id'";
$result = mysql_db_query($dbname,$sql);
$row = mysql_fetch_array($result);

if (!$row)
{
　　echo "该记录不存在";
　　echo "<p>SQL Query:$sql<p>";
　　exit;
}

echo "title<br>".$row[title]."<p>n";
echo "content<br>".$row[content]."<p>n";
echo "<p>SQL Query:$sql<p>";
?>

http://127.0.0.1/injection/show.php?id=1