Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean

[triad1234]

Let me put this straight.

I have a table : name_table

name varchar(10), meaning1 varchar(10), meaning2 varchar(10) ... meaning20 varchar(10).

 

#Note : The Fields Name & Meaning2 are already Filled.

 

Test.php (URL Passed : localhost/../test.php?name=some_name)

<?php
error_reporting(E_ALL);
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test_db";


// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
//Get name
$name = $_GET['name'];


$name_meanings = array(sometext1, sometext2, ... sometext19, sometext20);


for($k=1; $k<=20; $k++){
//check if the table cell is empty to be filled
$element_col = "meaning" . $k;
echo "</br>" . $element_col . "</br>";
$check = $conn->query("select $element_col from name_table WHERE name=$name");
if(!$check){
echo "</br> CHECK: False</br>";
$occurance = mysqli_num_rows($check); //Warning message pointing to this line
if($occurance == 0 ){
echo "</br>Occurance is 0</br>";
for($l=0; $l<sizeof($name_meanings); $l++){
$name_element = $name_meanings[$l];
$raw_pwd=$conn->query("insert into name_table($element_col) values($name_element) where name=$name");
}
}
else{
echo "</br>Meaning exists at $element_col</br>";
}
}
else{
echo "</br>Check is True</br>";
break;
}
}
?>

Output:

 

Meaning1

Check: False

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C:\\test.php on line 26

Occurrence is 0

 

Meaning2  <--This iteration went wrong

Check: False

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C:\\test.php on line 26

Occurrence is 0

.

.

.

Meaning20

Check: False

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C:\\test.php on line 26

Occurrence is 0

 

Question:

1. How do I put the warning, mysqli_num_rows() right?

2. Why is the PHP unable to detect the already inserted fields (meaning2)?

Any Suggestion.....Please.  

[kierany5]

If $check is false, then there is an issue with your query or MySQLi connection...

 

AND PLEASE, ESCAPE $name BEFORE PUTTING IT IN A QUERY.

 

You've just shown the world that your code may be susceptible to an SQL Injection...  (See http://php.net/manual/en/mysqli.real-escape-string.php for the function to use).

[mac_gyver]

the reason you are getting errors at the mysqli_num_rows() statement, is because your program logic is not correct and your query is failing due to an error of some kind. the $check variable will be a false value when the query fails due to an error. you are then trying to use that false value in the mysqli_num_rows($check) statement. your program logic should be testing if $check is a true value, without the !.

 

the reason your query is failing, is because you don't have single-quotes around the '$name' variable inside the sql statement.

 

finally, you don't need all that program logic anyway. you should not have a database table laid out like that. the data is not normalized, requiring you to write a ton of program logic to find, insert, update, or delete any of the data. you should instead have one row for each same meaning data item, not columns in a row for each same meaning data item.

[kierany5]

Following mac_gyver's reply, which I completely agree with, something like this is what you should do:

 

name_table:

id int(11) primary key auto increment

name varchar(10)

meaning varchar(10)

 

So it would hold data like:

1 | test | meaning1

2 | test | meaning2

3 | test | meaning3

4 | blah | meaning1

5 | blah | meaning2

6 | name | meaning 1

 

You could prioritise meanings by adding another column or putting them in order by ID.

 

Then just loop through like:

$check = $conn->query("select * from name_table WHERE name='".$conn->escape_string($name)."'");
while($row = $check->fetch_array())
{
 // Stuff here for each meaning
}

Edited February 11, 2015 by kierany5

[Tom10]

the reason you are getting errors at the mysqli_num_rows() statement, is because your program logic is not correct and your query is failing due to an error of some kind. the $check variable will be a false value when the query fails due to an error. you are then trying to use that false value in the mysqli_num_rows($check) statement. your program logic should be testing if $check is a true value, without the !.

 

the reason your query is failing, is because you don't have single-quotes around the '$name' variable inside the sql statement.

 

finally, you don't need all that program logic anyway. you should not have a database table laid out like that. the data is not normalized, requiring you to write a ton of program logic to find, insert, update, or delete any of the data. you should instead have one row for each same meaning data item, not columns in a row for each same meaning data item.

I agree

if(!check) {



}

That won't work, I would do:

if($check === FALSE) {



}

or 

if($check !== TRUE) {



}

[Tom10]

Also, you are vulnerable to SQL injection

//Get name
$name = $_GET['name'];

$check = $conn->query("select $element_col from name_table WHERE name=$name");

Sanitize the data with functions like real_escape_string, htmlspecialchars and htmlentities because you are also vulnerable to Cross Site Scripting.

 

i.e

//Get name
$name = $_GET['name'];
$name = htmlentities($name, ENT_QUOTES);
$name = htmlspecialchars($name, ENT_QUOTES);
$name = mysqli_real_escape_string($conn, $name);

If you are still getting errors after the advice you have been given then, use var_dump() and post the output on here.

var_dump($check);