mysql_num_rows error, but database is updated

Question

I have some PHP problems regarding my PHP code

I create function that update database, for changing password. Here's my syntax

function changePassword($username, $password, $salt){   
$query = "UPDATE mt_user SET password = '". $password ."' , salt = '". $salt . "' WHERE username = '". $username ."'";
$result = mysql_query($query);
    if ($result == false){
        $num_rows = mysql_error();
    } else {
        $num_rows = mysql_num_rows($result);
    }
mysql_close();
return $num_rows;
}

I try this function by create some script:

    echo changePassword('user1','test','test_salt');

The database value is updated but, the function is showing some warnings

Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in.....

What's wrong with the code? Because I don't see any errors.

score 3 · Accepted Answer · edited May 25 '19 at 14:21

3

mysql_num_rows() is the wrong function here because what is does

Retrieves the number of rows from a result set. This command is only valid for statements like SELECT or SHOW that return an actual result set.

To see how many rows were changed, use mysql_affected_rows().

$num_rows = mysql_affected_rows();

Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO, or MySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.

edited May 25 '19 at 14:21

Zoe

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answered Jun 30 '13 at 12:21

bwoebi

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hi, thanks for your information, yes i know i need to upgrade, but i still curious why this function is working but shows some warnings., now it's warning: Warning: mysql_affected_rows() expects parameter 1 to be resource, boolean given – randytan Jun 30 '13 at 12:25
@randytan don't pass any parameter to mysql_affected_rows… – bwoebi Jun 30 '13 at 12:25
i just change into mysql_affected_rows($result); the $num_rows is deleted, but still some warnings given – randytan Jun 30 '13 at 12:28
@randytan ___no___ parameters: `mysql_affected_rows();` (don't pass `$result`.) – bwoebi Jun 30 '13 at 12:29
i don't understand, please give some examples. – randytan Jun 30 '13 at 12:31
@randytan do ___not___ write `$num_rows = mysql_affected_rows($result);`. Write: `$num_rows = mysql_affected_rows();`! – bwoebi Jun 30 '13 at 12:32

score 1 · Answer 2 · answered Jun 30 '13 at 12:21

1

for update and insert queries you need to use mysql_affected_rows. mysql_num_rows only works for select statement.

answered Jun 30 '13 at 12:21

DevZer0

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i have try that but it getting me new warnings: Warning: mysql_affected_rows() expects parameter 1 to be resource, boolean given – randytan Jun 30 '13 at 12:25
that means the query is failing. – DevZer0 Jun 30 '13 at 12:26
the database is updated devzer, but the function shows some warnings. – randytan Jun 30 '13 at 12:27
change your query execution to `$result = mysql_query($query) or die(mysql_error());` and see what happens. – DevZer0 Jun 30 '13 at 12:32

score 0 · Answer 3 · answered Jun 30 '13 at 14:11

A little advice: replace mysql to mysqli. It's more secure. This example is with this one.

function changePassword($username, $password, $salt){   
$query = "UPDATE mt_user SET password = '". $password ."' , salt = '". $salt . "' WHERE username = '". $username ."'";
$result = mysqli_query($connection,$query);
    if ($result){
    $num_rows = mysqli_affected_rows($connection);        
    } else {
        $num_rows = mysqli_error($connection);
    }
mysql_close();
return $num_rows;
}

mysql_num_rows error, but database is updated

3 Answers3