How to Perform Data Validation using wpdb in WordPress Plugin
Posted on 19th June 2023
Data validation is critical for any WordPress plugin that processes data from users. In this article, we’ll show you how to properly validate data using the wpdb class.
The wpdb class is the class used by WordPress to interact with databases. It is possible to use other database interaction classes, but wpdb is the most common and most supported.
When you use the wpdb class to validate data, there are two things you need to keep in mind:
1. The data you are validating must be in the correct format.
2. The data you are validating must be sanitized before it is stored in the database.
The correct format for data depends on the type of data you are processing. For example, if you are processing a date, the data must be in YYYY-MM-DD format. If you are processing an email address, the data must be in a valid email format.
The data must also be sanitized before it is stored in the database. Sanitization is the process of removing any invalid characters from the data. For example, if you are processing a date, you would want to remove any characters that are not numbers or dashes.
To sanitize data, you should use the wp_kses() function. This function will remove any invalid characters from the data.
Once the data is in the correct format and has been sanitized, you can then use the wpdb class to insert the data into the database.
To insert data into the database, you will need to use the insert() or update() method of the wpdb class. Both of these methods take an array of data as their first argument. The array should be in the format of field => value.
For example, if you were inserting data into the post_title field of the posts table, the array would be in the format of ‘post_title’ => ‘My Title’.
Once the data has been inserted into the database, you can then use the get_var() or get_row() methods of the wpdb class to retrieve the data.
The get_var() method will return a single value from the database. The get_row() method will return a single row from the database.
Both of these methods take the SQL query as their first argument. The SQL query should be a SELECT query.
For example, if you wanted to retrieve the post_title field from the posts table, the SQL query would be ‘SELECT post_title FROM posts’.
Both of these methods also take an array of data as their second argument. This array should be in the format of field => value.
For example, if you wanted to retrieve the post with the ID of 1, the array would be in the format of ‘ID’ => ‘1’.
Once the data has been retrieved from the database, you can then use the wp_kses() function to sanitize the data.
After the data has been sanitized, you can then use the echo or print statement to output the data.
That’s all there is to data validation using the wpdb class. By following these steps, you can ensure that your data is in the correct format and is sanitized before it is stored in the database.
When you are validating data, you are essentially checking that the data is correct and meets all the requirements that you have set. There are many ways to validate data, but one of the most common and effective ways is to use the wpdb class in WordPress.
The wpdb class is designed to abstract away the details of database interactions and make it easy to run queries and get results. It also provides a number of helper functions for validating data.
To use the wpdb class, you first need to include the class file:
Once you have included the class file, you can create an instance of the wpdb class:
$wpdb = new wpdb( ‘username’, ‘password’, ‘database’, ‘localhost’ );
You will need to replace the ‘username’, ‘password’, ‘database’, and ‘localhost’ with the appropriate values for your environment.
Once you have an instance of the wpdb class, you can use the various methods it provides to validate data.
The first method we will look at is the wpdb::check_connection() method. This method will check that a database connection can be made and that the WordPress tables are present in the database.
If the check_connection() method returns false, then you know that there is a problem with the database connection or the WordPress tables are not present.
The next method we will look at is the wpdb::query() method. This method can be used to run any SQL query. It is important to note that you should not use this method to run untrusted SQL queries.
If you do use this method to run untrusted SQL queries, you open up your website to SQL injection attacks.
The wpdb::query() method takes two parameters: the SQL query to run, and an array of values to substitute into the query.
The values in the array will be sanitized before they are substituted into the query. This sanitization includes escaping characters that have a special meaning in SQL, such as single quotes.
Once the query has been run, the method will return a boolean value indicating whether or not the query was successful.
The next method we will look at is the wpdb::get_results() method. This method can be used to run a SQL query and return the results as an array.
The wpdb::get_results() method takes two parameters: the SQL query to run, and an array of values to substitute into the query.
Like the wpdb::query() method, the values in the array will be sanitized before they are substituted into the query.
The method will return an array of objects. Each object in the array will contain the columns from the SQL query as properties.
The next method we will look at is the wpdb::get_var() method. This method can be used to run a SQL query and return a single value from the results.
The wpdb::get_var() method takes two parameters: the SQL query to run, and an array of values to substitute into the query.
Like the other methods we have looked at, the values in the array will be sanitized before they are substituted into the query.
The method will return the value of the first column in the first row of the SQL query results.
The next method we will look at is the wpdb::get_row() method. This method can be used to run a SQL query and return a single row from the results.
The wpdb::get_row() method takes two parameters: the SQL query to run, and an array of values to substitute into the query.
Like the other methods we have looked at, the values in the array will be sanitized before they are substituted into the query.
The method will return an object containing the columns from the SQL query as properties.
The next method we will look at is the wpdb::get_col() method. This method can be used to run a SQL query and return a single column from the results.
The wpdb::get_col() method takes two parameters: the SQL query to run, and an array of values to substitute into the query.
Like the other methods we have looked at, the values in the array will be sanitized before they are substituted into the query.
The method will return an array containing the values from the first column of the SQL query results.
The next method we will look at is the wpdb::prepare() method. This method can be used to prepare a SQL query for execution.
The wpdb::prepare() method takes two parameters: the SQL query to prepare, and an array of values to substitute into the query.
Like the other methods we have looked at, the values in the array will be sanitized before they are substituted into the query.
The method will return a sanitized SQL query string that can be executed using the wpdb::query() method.
The wpdb class also provides a number of other methods that can be used for data validation. These methods are: wpdb::insert(), wpdb::update(), wpdb::delete(), and wpdb::replace().
These methods can be used to insert, update, delete, or replace data in the WordPress database.
Each of these methods takes two parameters: an array of data to insert, update, delete, or replace, and an array of values to substitute into the query.
Like the other methods we have looked at, the values in the array will be sanitized before they are substituted into the query.
These methods will return a boolean value indicating whether or not the data was inserted, updated, deleted, or replaced successfully.
The wpdb class also provides a number of other methods that are not directly related to data validation. These methods include: wpdb::escape(), wpdb::strip_invalid_text(), wpdb::strip_invalid_characters(), and wpdb::check_mysql_version().
These methods can be used to escape data for use in SQL queries, strip invalid characters from data, or check the version of MySQL that is being used.
In conclusion, the wpdb class provides a number of methods that can be used to validate data. These methods can be used to insert, update, delete, or replace data in the WordPress database.
