If you're working with MySQL databases and PHP, you might have come across the mysqli_num_rows() error at some point. This error occurs when you try to use the mysqli_num_rows() function to count the number of rows in a MySQL query result, but you pass in the wrong type of parameter.
In this guide, we'll explain what causes this error, and provide a step-by-step solution to help you fix it.
What Causes the mysqli_num_rows() Error?
The mysqli_num_rows() function is used to count the number of rows in a MySQL query result. To use this function, you need to pass in a mysqli_result object as the parameter.
However, if you pass in something else, such as a string or an integer, you'll get the mysqli_num_rows() error message:
Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in /path/to/your/script.php on line xx
This error message indicates that the parameter you passed in is not a mysqli_result object, but a boolean value (true or false).
How to Fix the mysqli_num_rows() Error
To fix the mysqli_num_rows() error, you need to make sure that you're passing in the correct parameter to the function. Here are the steps to follow:
Step 1: Check Your Query
First, you need to check your MySQL query to make sure that it's returning a mysqli_result object. If your query is incorrect, it won't return the expected result set, and you'll get the mysqli_num_rows() error.
Here's an example query that should return a mysqli_result object:
$query = "SELECT * FROM users";
$result = mysqli_query($connection, $query);
If your query is correct, you should see a mysqli_result object stored in the $result variable.
Step 2: Check Your Code
Next, you need to check your code to make sure that you're passing in the correct parameter to the mysqli_num_rows() function.
Here's an example of how to use the mysqli_num_rows() function correctly:
$query = "SELECT * FROM users";
$result = mysqli_query($connection, $query);
$count = mysqli_num_rows($result);
In this example, we're passing in the $result variable, which contains a mysqli_result object, to the mysqli_num_rows() function.
If you're still getting the mysqli_num_rows() error, double-check your code to make sure that you're passing in the correct parameter.
Step 3: Debug Your Code
If you've checked your query and your code, and you're still getting the mysqli_num_rows() error, you might need to debug your code to find the problem.
Here are a few things to check:
- Make sure that your database connection is working correctly.
- Check that your query is returning the expected result set.
- Make sure that you're using the correct variable names and data types in your code.
FAQ
Q1: What is a mysqli_result object?
A1: A mysqli_result object is a PHP object that represents a MySQL query result set. You can use this object to fetch rows from the result set, count the number of rows, and perform other operations on the result set.
Q2: Why am I getting the mysqli_num_rows() error?
A2: You're getting the mysqli_num_rows() error because you're passing in the wrong type of parameter to the function. You need to pass in a mysqli_result object, but you're passing in something else, such as a string or an integer.
Q3: How do I know if my query is returning a mysqli_result object?
A3: You can use the mysqli_query() function to execute your query and store the result in a variable. If your query is correct, you should see a mysqli_result object stored in the variable.
Q4: What should I do if my query is not returning a mysqli_result object?
A4: If your query is not returning a mysqli_result object, you need to check your query to make sure that it's correct. Make sure that your query is syntactically correct and that it's returning the expected result set.
Q5: Can I use mysqli_num_rows() with prepared statements?
A5: Yes, you can use mysqli_num_rows() with prepared statements. After executing a prepared statement, you can use mysqli_stmt_store_result() to store the result set in memory, and then use mysqli_stmt_num_rows() to count the number of rows in the result set.
Conclusion
The mysqli_num_rows() error can be frustrating to deal with, but it's usually easy to fix once you know what's causing it. By following the steps outlined in this guide, you should be able to fix this error and get your code working again. Remember to always check your query and your code, and to debug your code if necessary.