How can the use of mysqli_num_rows() in PHP lead to the warning "expects parameter 1 to be mysqli_result, boolean given"?

When using mysqli_num_rows() in PHP, the warning "expects parameter 1 to be mysqli_result, boolean given" can occur when the query executed by mysqli_query() returns a boolean false instead of a mysqli_result object. This can happen if the query fails for some reason. To solve this issue, you should first check if the query was successful before using mysqli_num_rows().

$result = mysqli_query($conn, $query);

if($result) {
    $row_count = mysqli_num_rows($result);
    // Use $row_count as needed
} else {
    // Handle query failure
}