转账余额[重复]

Question

This question is an exact duplicate of:

• MYSQL transfer same or less than balance [closed] 1 answer

I am building a site where users can transfer funds to one another.

I have my code working so each user can send funds, however i'm not sure how to only let them transfer what they have.. (if they have 10 cant send 11)

See code below

$result = mysql_query("UPDATE member
SET balance = IF(personID = $accountfrom, balance-$amount, balance+$amount)
WHERE personID IN ($accountfrom, $accountto)")
 or die(mysql_error());

Can anyone help with this??

UPDATED

$select_result = $mysqli->query("SELECT * FROM member where personID="$accountfrom" ");
while ($select = mysqli_fetch_assoc($select_result)) {
   $balance=$select['amount'];
   if($balance=>$balance){
       $result = mysql_query("UPDATE member
       SET balance = IF(personID = $accountfrom, balance-$amount, balance+$amount)
       WHERE personID IN ($accountfrom, $accountto)")
       or die(mysql_error());
   }
}

Shows error:

Parse error: syntax error, unexpected T_VARIABLE in >/home/u704855438/public_html/transfer.php on line 264

Line 266 is if($balance=>$amount){

</div>

Answer 1

Just check in your database wether the amount he wants to transfer is lower or the same as the amount he has. If it doesn't dont transfer it (so dont do anything and show an error message) Just put an

if($amount_in_database>=$amount_he_wants_to_transfer){

}

around your update query.

To get the amount in the database do this:

$select_result = $mysqli->query("SELECT * FROM member where personid='$accountfrom' ");

Afterwards use this where ['amount'] should be your column with the funds:

while ($select = mysqli_fetch_assoc($select_result)) {
$amount_in_database=$select['amount'];
}

So this would be your code:

$select_result = $mysqli->query("SELECT * FROM member where personid=$accountfrom ");
while ($select = mysqli_fetch_assoc($select_result)) {
   $amount_in_database=$select['amount'];
   if($amount_in_database>=$amount_he_wants_to_transfer){
       $result = $mysqli->query("UPDATE member
       SET balance = IF(personID = $accountfrom, balance-$amount, balance+$amount)
       WHERE personID IN ($accountfrom, $accountto)");

   }
}