PHP in Templates and Template Conditionals

[dexon95]

Hi, i need help with this code :

$balance = mysql_query("SELECT `balance` FROM iconomy WHERE `username` = '{$mybb->user[\'fid4\']}'");
echo mysql_real_escape_string($balance); 

Cause MyBB is telling me it have a security issue :/
And i don't really see how i can fix it

Can you help me please ?