如何在php预处理语句中显示值

Question

I have the following query and I want to print the "total" I want to print the total like I print "num_rows" How can I do that ?

$stmt = $conn->prepare("SELECT SUM( total) AS total FROM money");
            $stmt->execute();
            $stmt->store_result();
            print $stmt->total;

my table structure are like this

id user monthly_pay total
1  Adam  1500       1500
2  Erik 1500       1500 
3  Mark  1500      1500
4 Gusta 1500       1500
5  Mike 1500       1500

I want to view the total "75000"

Answer 1

It's strictly not needed to use prepared statements when not dealing with user-input, but there's no disadvantage using it either (should you expand the query to deal with variables/user-input, the ground-work is already done!). This means for a static query like this, you can just use normal query() functions.

However, using prepared statements like this, you need to bind the result and fetch it. Using $stmt->num_rows is going to trick you, as this will return the amount of rows returned by the query - which will only be 1. It will not return the result.

The snippet below has been modified to use bind_result() and fetch(). This will prepare the query, bind the results to $sum and fetch it.

$stmt = $conn->prepare("SELECT SUM( total) AS total FROM money");
$stmt->execute();
$stmt->bind_result($sum);
$stmt->fetch();
print "The sum is ".$sum;

References

• http://php.net/manual/en/mysqli-stmt.bind-result.php
• http://php.net/manual/en/mysqli-stmt.fetch.php