php – SQL select语句中的语法错误

我的php文件是：

<?php

ini_set('default_charset','utf-8');
header('Content-Type: text/html; charset=UTF-8');



mysql_connect("localhost","root","");
mysql_select_db("farm_o_pedia");

mysql_set_charset('utf8');
$result1 = mysql_query("SET NAMES utf8");

$lang=$_POST['LanguageName'];

$query1="select lang_id from lang_selection where lang_name='$lang'";
$lang_id=mysql_query($query1) or die(mysql_error());


$query2="select crop_name from crop_master where lang_id=$lang_id";
$result2=mysql_query($query2) or die(mysql_error());

while($row=mysql_fetch_assoc($result2))
{
    $output[]=$row;
}

print(json_encode($output));

mysql_close();

?>

我在Logcat中遇到这种错误：

02-16 22:08:04.216: I/HTTP ok(1251): org.apache.http.message.BasicHttpResponse@4052f0b8
02-16 22:08:04.216 : I/JsonObj(1251): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘id #4’ at line 1

我不知道我的语法有什么问题.

EDIT: Used PDO as suggested and its working fine:
This is my new script.

<?php


$db = new PDO('mysql:host=localhost;dbname=farm_o_pedia;charset=utf8','root','');

$db->query("SET NAMES utf8");

$lang=$_POST['LanguageName'];

$query1="select crop_name from crop_master where lang_id=(select lang_id from lang_selection where lang_name='$lang')";

$result2=$db->query($query1);

while(($row=$result2->fetch(PDO::FETCH_ASSOC))!=false)
{
    $output[]=$row;
}

print(json_encode($output));

$db=null;

?>