警告：mysql_num_rows（）期望参数1是资源，第17行/var/customers/webs/ni272979_1/Loader/login.php中给出的布尔值[重复]

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• ERROR: Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\…\…php on line 19 7 answers
• Reference - What does this error mean in PHP? 34 answers

<?php
$filename = 'install.php';
if (file_exists($filename)) {
echo ("<center><font color='red'><b>/install.php still exists<br>
After installing please delete install.php</center></font></b>");
} else {
if (isset($_POST['Login'])){
include('config.php');
    if (!mysql_connect($host, $username, $password)) die("Can't connect to database");
    if (!mysql_select_db($db_name)) die("Can't select database");
    $myusername=$_POST['myusername'];
    $mypassword=$_POST['mypassword'];

    $sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword' or die(mysql_error());";
    $result=mysql_query($sql);
    $count=mysql_num_rows($result);
    if($count >= 1){
    session_register("myusername");
    session_register("mypassword");
    header("location: index.php");
    } else {

    }
}

?>

I have tried to fix it but not sucsessfuly. I don't know how i can fix it because i am a php noob.

</div>

Answer 1

You have an error in your query. It should be something like this.

$sql = "SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword';";

And then you can do something like this.

 $result=mysql_query($sql) or die(mysql_error());

Also try using MySQLi or PDO function for CRUD operations.