关于PHP的几个疑问关于PHP

<?php
$con = mysqli_connect('localhost','root','123456');
if($con){
echo '链接数据库成功！';
}else{
echo mysql_error();

};
mysql_select_db('test');
mysql_set_charset('utf8');
$sql="SELECT * FROM t2 ";
$result=mysql_query($sql,$con);
if($result)
{
echo '查询成功';
}
else{
echo mysql_error();
}

?>
数据库已经连接成功，但是为什么在执行查询语句的时候，却会报错了？
链接数据库成功！Access denied for user 'ODBC'@'localhost' (using password: NO)

https://blog.csdn.net/lina_999/article/details/87797322

你可以试一下此代码，已纠错
<?php
$con = mysqli_connect('localhost','root',''123456);
if($con){
echo '链接数据库成功！';
}else{
echo mysqli_error($con);
};
mysqli_select_db($con,'test');
$charset="set names utf8";
mysqli_set_charset($con, $charset);
$sql="SELECT * FROM t2";
$result=mysqli_query($con, $sql);
if($result){
echo '查询成功';
}else {
echo mysqli_error($con);
}
?>