使用PHP从MySQL中选择并回显单个字段

Question

I'm trying to select and echo a single field.

This is my code when I'm trying it

session_start();
$query = "select id from user where username = ".$_SESSION['username'];
$result = mysql_query($query);
$admin_id = mysql_fetch_array($result);
echo $admin_id['id'];

When I run that code, this warning text appears

mysql_fetch_array() expects parameter 1 to be resource, boolean given in ......

How should I do it?

Answer 1

You should use quotes when you assign values in sql queries .

$query = "select id from user where username = '{$_SESSION['username']}'";

Or

$query = "select id from user where username = '" . $_SESSION['username'] . "'";

However, it is not a good practice so you better look forward prepared statements to reduce sql injection vulnerability : http://ru2.php.net/pdo.prepared-statements