my problem is that whatever symbol i write in sell_form.php even if it doesn't exist in portfolio table. the query return true.here's the query in sell.php
and that's sell_form.php
<form action = "sell.php" method = "post" >
<input class="form-control" type = "text" name = "symbol"/>
<input class="btn btn-default" type = "submit" placeholder = "sell"/>
</form>
