please help me to clear the error "Parse error: syntax error, unexpected '$blood' (T_VARIABLE) in C:\xampp\htdocs\site\profile\profile.php on line 12"

Question

This is the code I am using

The code is given below 
<?php
if(isset($_POST['bg']))
{
$blood=$_POST['bg'];
$con = mysqli("localhost","root","","test");
if($con->connect_error)
{
die("Failed to connect : ".$con->connect_error);
}
else
{
$sql = ("SELECT * FROM donor WHERE bg = '"$blood"';");
$res = mysqli_query($con,$sql);
$resuch = mysqli_num_rows($res);
    if($resuch > 0 )
    {
        while ($row = mysqli_fetch_assoc($res))
        {
        echo $row['usr']. "<br>";
        }
    }
}
}
?>

It arises an error: Parse error: syntax error, unexpected '$blood' (T_VARIABLE) in C:\xampp\htdocs\site\profile\profile.php on line 12