Trying to get property of non-object from mysqli's num_rows

Question

$conn = mysqli_connect($dbhost, $dbuser, $dbpass,$Database);
$sql="Select  from Tutorial_tbl where tutorial_title=".$tutorial_title;
$res=$conn->query($sql);

if($res->num_rows!=0){
    while($row=$res->fetch_assoc()){
      echo"<tr><td>".$row["tutorial_title"];#."</td><td>".$row["tutorial_author"]."</td><td>".$row["submission_date"]."</td></tr>";
    }
}
$conn->close();

Why am I getting this error?

Trying to get property of non-object

Possible duplicate of [Reference - What does this error mean in PHP?](https://stackoverflow.com/questions/12769982/reference-what-does-this-error-mean-in-php) — faintsignal, Sep 25 '18 at 03:11

score 1 · Answer 1 · answered Aug 02 '17 at 18:39

1

If the value of $tutorial_title is a string must be into '', like this "SELECT * FROM Tutorial_tbl WHERE tutorial_title= '$tutorial_title'"; also, your query it's wrong, it's not SELECT FROM but SELECT * FROM, your query fails and dont build the object then when you try to access to num_rows field PHP throws you an exception.

answered Aug 02 '17 at 18:39

Max Almonte

59
4

But nothing happened from your answer. I forgot a * before from but it don't work – Sanjeev Chauhan Aug 03 '17 at 18:05

score 0 · Answer 2 · answered Sep 25 '18 at 11:41

You are connecting with procedural syntax, then performing all query processes with object-oriented syntax. Choose one style and stick with it - I recommend OO all the way through.
Using all caps for mysql keywords will improve the readability of your queries, and is generally good practice.
You have not declared the three targeted columns in your SELECT clause. This is a query killer.
$tutorial_title if a trusted value (not from a user submission) and cannot possibly contain a single quote, should be wrapped in single quotes. If the value may contain a single quote or comes from an insecure source, you should use a prepared statement with a placeholder and a bound variable.
To help you with debugging, check for a false result from your query. - You don't need to count the rows unless you are going to display a special message which states that there were no rows found.
The while loop will only iterate if there is something to iterate, so it is a safe call.
The ;# in your echo line will only cause trouble, remove it.

My recommended/untested code:

if (!$conn = new mysqli($dbhost, $dbuser, $dbpass, $Database)) {
    echo "connection error";  // $conn->connect_error;
} elseif (!$stmt = $conn->prepare("SELECT tutorial_title, tutorial_author, submission_date FROM Tutorial_tbl WHERE tutorial_title = ?")) {
    echo "query syntax error";  // $conn->error;
} elseif (!$stmt->bind_param("s", $tutorial_title) || !$stmt->execute() || !$stmt->bind_result($title, $author, $date)) {
    echo "statement error"; // $stmt->error;
} else {
    echo "<table>";
        echo "<tr><th>Title</th><th>Author</th><th>Date</th></tr>";
        while ($stmt->fetch()) {
            echo "<tr><td>$title</td><td>$author</td><td>$date</td></tr>";
        }
    echo "</table>";
    $stmt->close();  // optional
    $conn->close();  // optional
}

In the above snippet, I've baked in falsey conditional checks at each point to enable simple debugging. I have commented out the error functions, so that this code could be copy-pasted. Just be aware that you must never show the actual error messages to a public audience as a matter of security.

Using bind_result() is very handy when you know exactly which columns you will be returning -- the display syntax is very clean.

Trying to get property of non-object from mysqli's num_rows

2 Answers2