Having problem with error mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given

Question

1.00/5 (1 vote)

See more:

mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given in C:\laragon\www\studentfee\015proc_search2.php on line 25

What I have tried:

PHP

<?php

$searchtype=$_POST['searchtype'];
$searchterm=$_POST['searchterm'];
$searchterm= trim($searchterm);

if (!$searchtype || !$searchterm)
{
	echo ' Please Enter your search. Please enter again.';
	exit;
}

include ('001link_db2.php');
$query = "select * from v_student_fee LIKE '%$searchterm'";
$result = mysqli_query($conn,$query);
$num_results = mysqli_num_rows($result);
echo "<center>";
echo '<p>The numbers: '.$num_results.'</p>';

?>
<P><center> List</center>  
<table border="1" width="849" align="center" cellspacing="2" cellpadding="2">
<tr>
<td align="center" bgcolor="#FFCC00">ID</td>
<td align="center" bgcolor="#FFCC00">Student Name</td>
<td align="center" bgcolor="#FFCC00">Total Fees</td>


</tr>
<?PHP

for ($i=0; $i <$num_results; $i++)
{
 $row = mysqli_fetch_all($result);
 echo "<tr>";
 echo "<td>" .$row["id"]. "</td>";
 echo "<td>" .$row["student_name"].  "</td>";
 echo "<td>" .$row["total_fees"]."</td>";

}
echo "</table>";
echo "<center>";
echo "<br>";
 

 ?>

Posted 8-Feb-22 20:14pm

Nurul Hazrani

Updated 9-Feb-22 9:05am

Sean Ewington

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard MacCutchan · Accepted Answer · 2022-02-08T21:17:00

Solution 2

If you check the documentation for PHP: mysqli::query - Manual[^] you will clearly see that when the query statement fails the call returns the boolean value FALSE. Do not assume that your API calls always do what you think; check the return values first.

Posted 8-Feb-22 21:17pm

Richard MacCutchan

OriginalGriff · Accepted Answer · 2022-02-08T20:24:00

Look at your SQL:

$query = "select * from v_student_fee LIKE '%$searchterm'";

There are two problems with it:
1) It's not valid SQL syntax.
2) It's very dangerous.

The syntax of a basic SELECT is simple:

SQL

SELECT * FROM MyTable WHERE MyColumn LIKE '%123'

Yours is missing the WHERE keyword, and the column name ... SQL will not "Guess what you mean", you have to explicitly tell it.

And never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?