How to Sanitize and Validate Data with wpdb in WordPress Plugin

Posted on 17th June 2023

When developing a WordPress plugin, you’ll often need to sanitize and validate data. This can be done with the WordPress $wpdb class. In this article, we’ll show you how to sanitize and validate data with $wpdb.

What is wpdb?

$wpdb is the WordPress class for interacting with a database. It can be used to sanitize and validate data. To use $wpdb, you’ll need to include the following code in your plugin:

global $wpdb;
$wpdb = new wpdb(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);

You’ll also need to replace DB_USER, DB_PASSWORD, DB_NAME, and DB_HOST with your database credentials.

How to Sanitize Data with wpdb

To sanitize data, you’ll need to use the $wpdb->prepare() method. This method takes two parameters: the SQL query and an array of variables. The variables in the array will be sanitized and replaced in the SQL query. For example, if you have the following SQL query:

$sql = "INSERT INTO table (column1, column2) VALUES (%s, %s)";

You can sanitize the data like this:

$data = array(
  'value1',
  'value2',
);

$wpdb->query($wpdb->prepare($sql, $data));

The $wpdb->prepare() method will sanitize the $data array and replace the %s placeholders in the SQL query with the sanitized data. You can also use the $wpdb->escape() method to sanitize data before inserting it into the database.

How to Validate Data with wpdb

To validate data, you’ll need to use the $wpdb->get_var() method. This method takes two parameters: the SQL query and an array of variables. The variables in the array will be replaced in the SQL query. The $wpdb->get_var() method will then return the first column of the first row of the result set. For example, if you have the following SQL query:

$sql = "SELECT COUNT(*) FROM table WHERE column1 = %s";

You can validate the data like this:

$data = array(
  'value1',
);

$count = $wpdb->get_var($wpdb->prepare($sql, $data));

if ($count > 0) {
  // the data is valid
} else {
  // the data is invalid
}

In the example above, the $wpdb->get_var() method will return the number of rows in the table where column1 is equal to value1. If the number of rows is greater than 0, the data is valid. If the number of rows is 0, the data is invalid.

Conclusion

In this article, we showed you how to sanitize and validate data with $wpdb. We hope this article has been helpful.

The $wpdb class provides a simple method for sanitizing data before inserting it into the WordPress database.

All data sanitization methods in the $wpdb class are based on the PHP function filter_var(), which provides a flexible way to validate and sanitize data.

The first parameter of the $wpdb::sanitize() method is the data to be sanitized. The second parameter is the data type. The third parameter is an optional array of options.

The $wpdb::sanitize() method can be used to sanitize a variety of data types, including:

string: A string of characters. This is the default data type.
url: A URL. The $wpdb::sanitize() method will automatically add the http:// protocol if it is not present in the URL.
email: An email address. The $wpdb::sanitize() method will automatically add the mailto: protocol if it is not present in the email address.
int: An integer.
float: A floating point number.
bool: A boolean value (true or false).
array: An array of values. The $wpdb::sanitize() method will automatically serialize the array if necessary.
object: An object. The $wpdb::sanitize() method will automatically serialize the object if necessary.

The $wpdb::sanitize() method can be used to sanitize data for insertion into the database, or for display on the front-end of a WordPress site.

When sanitizing data for insertion into the database, it is important to use the appropriate data type. For example, if a field in the database is an integer, the data should be sanitized as an integer. If the data is a string, it should be sanitized as a string.

When sanitizing data for display on the front-end, the data type is less important. However, it is still best practice to use the appropriate data type.

The $wpdb::sanitize() method can also be used to validate data. The method will return false if the data is not of the specified data type.

The $wpdb::sanitize() method is not the only way to sanitize and validate data. The $wpdb::check_invalid_utf8() method can be used to check for invalid UTF-8 characters in a string.

The $wpdb::strip_invalid_text() method can be used to remove invalid characters from a string. This method is useful for removing invalid characters from a string before inserting it into the database.

The $wpdb::strip_invalid_ascii() method can be used to remove invalid ASCII characters from a string. This method is useful for removing invalid characters from a string before displaying it on the front-end.

Sanitizing and Validating Data With wpdb

When it comes to data sanitization and validation, the WordPress Database API (wpdb) is your friend. wpdb provides a set of helper functions that make it easy to clean and validate user-provided data before adding it to your database.

To sanitize data, you should use the wpdb::prepare() method. prepare() takes a SQL query with placeholders as its first argument, and an array of data to sanitize as its second argument. prepare() will then sanitize the data and insert it into the query in the appropriate placeholders.

For example, say you have a form on your website that allows users to submit their email address. You want to store this email address in your database, but you first need to sanitize it to protect against malicious input. You can do this with prepare():

$email = ‘some@example.com’;

$wpdb->prepare( “INSERT INTO my_table (email) VALUES (%s)”, $email );

The %s in the query is a placeholder for a string value. prepare() will sanitize the $email variable and insert it into the query in the %s placeholder.

You can also use prepare() to sanitize data for use in a WordPress shortcode:

function my_shortcode( $atts ) {

extract( shortcode_atts( array(

‘id’ => 0

), $atts ) );

if ( ! $id )

return;

$id = $wpdb->prepare( “%d”, $id );

// do something with $id

}

add_shortcode( ‘my_shortcode’, ‘my_shortcode’ );

In the example above, the $id variable is first sanitized with prepare() before being used in the my_shortcode() function.

In addition to sanitizing data, you may also need to validate it. For example, you may want to check that an email address submitted by a user is in a valid format. WordPress provides the is_email() function for this purpose:

$email = ‘some@example.com’;

if ( is_email( $email ) ) {

// $email is a valid email address

} else {

// $email is not a valid email address

}

You can also use is_email() to validate data before adding it to your database:

$email = ‘some@example.com’;

if ( is_email( $email ) ) {

$wpdb->insert(

‘my_table’,

array(

’email’ => $email

)

);

}

The WordPress Database API is a powerful tool for sanitizing and validating data. By using the wpdb::prepare() method and the is_email() function, you can easily protect your data from malicious input.

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