mysql_real_escape_string
just takes a string for an argument. That's it.
$string = mysql_real_escape_string('string')
If you want to specify the link identifier, it is the optional second argument:
$string = mysql_real_escape_string('string', $dbc)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…