PHP mySQL Error
Im new to php so I decided to follow this tutorial for a simple login screen. I got the code setup but when I try login I get this error:
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in (a long file path to the script) on line 27
The code I got from the tutorial is:
<?php
ob_start();
$host="thehost"; // Host name
$username="myusername"; // Mysql username
$password="mypass"; // Mysql password
$db_name="test"; // Database name
$tbl_name="members"; // Table name
// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// Define $myusername and $mypassword
$myusername=$_POST['myusername'];
$mypassword=$_POST['mypassword'];
// To protect MySQL injection (more detail about MySQL injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);
$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);
// If result开发者_如何学Go matched $myusername and $mypassword, table row must be 1 row
if($count==1){
// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword");
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}
ob_end_flush();
?>
(Note: All of the mySQL database info is filled in on my version)
Aslo, the author gives a php5 version and a normal php version. I have tried both and gotten the same error. If anyone knows why this is happening help is really appreciated.
You can print the $sql
variable and try the query yourself, or print the mysql error with mysql_error()
.
This query seems to fail.
You need to check the return from mysql_query()
; you can't assume it worked. If it's FALSE
, call mysql_error()
to get the error message from MySQL
this is how i do my DB access in PHP:
$result=mysql_query($sql) or die ("bad sql query: ".mysql_error());
so if the SQL is wrong; i get a usable error, usually with the guilty SQL fragment
The problem is that mysql_num_rows
expects a resource object but if no results are found, it'll just be null. Instead of counting the rows that way, just check if $result === null
.
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