Mysqli_num_rows() expects parameter 1 to be mysqli_result, bool [somebody solve this]

Question

1.00/5 (1 vote)

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PHP

<?php
include "test.php";
 ?>
 
<html>

<head>
    <title>Login </title>
</head>

<body>
	<form name="login_form" class="form-vertical" action="" method="post">
		<h3>Login Page</h3>
		Username: <input type="text" name="username" required/>
		Password: <input type="password"  name="password" required/>
		<center>
            <input type="submit" name="submit_1" value="Login" />
        </center>
	 </form>
	<?php
		if (isset($_POST["submit_1"]))
		{
			$username=$_POST["username"];
			$password=$_POST["password"];
			$count=0;
			$sql="select * from employee where username='$username'&& password='$password'";
			$res=mysqli_query($conn,$sql);
			$count=mysqli_num_rows($res);
			if($count>0&&!$res)
			{
			 header("Location:index.php");
			}
			else
            {
        ?>
		<div>Invalid Username or Password</div>
    <?php
            }

	}
    ?>
</body>

</html>

What I have tried:

It always shows "Invalid Username or Password".

Posted 28-Sep-20 1:54am

Akhil Mathew

Updated 28-Sep-20 2:14am

CPallini

v3

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Comments

Richard Deeming 28-Sep-20 8:34am

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation / interpolation to build a SQL query. ALWAYS use a parameterized query.

PHP: SQL Injection - Manual[^]

Richard Deeming 28-Sep-20 8:35am

You're storing passwords in plain text. NEVER do that.
Secure Password Authentication Explained Simply[^]

PHP even has built-in functions to help you do the right thing:
PHP: password_hash[^]
PHP: password_verify[^]

Richard Deeming 28-Sep-20 8:36am

MySQL :: MySQL 8.0 Reference Manual :: 12.4.3 Logical Operators[^]
"The && operator is a nonstandard MySQL extension. As of MySQL 8.0.17, this operator is deprecated and support for it will be removed in a future MySQL version."

2 solutions

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Richard MacCutchan · Answer 1 · 2020-09-28T02:03:00

Solution 1

Most likely because the username and password are not found in the database. And the error message confirms it: see Mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in[^].

Posted 28-Sep-20 2:03am

Richard MacCutchan

Comments

CPallini 28-Sep-20 8:15am

5.

CPallini · Answer 2 · 2020-09-28T02:15:00

Solution 2

As already noted by Richard, your query failed. See, for instance PHP mysqli query() Function[^] (have a look at 'return value' section).
You have to test the $res value, before calling mysqli_num_rows($res), e.g.

PHP

if ( $res )
{
  $count=mysqli_num_rows($res);
  //...
}
else
{
  // handle here the query failure
}

Posted 28-Sep-20 2:15am

CPallini

v2

Comments

Richard MacCutchan 28-Sep-20 9:06am

5 for you. I wonder how many more times we will need to post this answer?

CPallini 29-Sep-20 2:07am

:-)
Thank you, Richard.