Have you tried wpcf7_before_send_mail? I found cf7_external_db2018.php in Github (by mheywood90). This version is updated for WP 4.9.
function wpcf7_send_to_external ( $cf7 ) {
//external db details
$username = 'username';
$password = 'password';
$database = 'database';
$host = 'host_ip';
//create new wpdb instance
$mydb = new wpdb($username, $password, $database, $host);
//limit hook to only fire on particular form ID (optional)
if ( $cf7->id == 1 ) {
//get select box for different enquiry types (optional)
$type = $cf7->posted_data["your-select"];
//if form type is equal to above value (optional)
if ( $type == 'Form Name' ){
//code added for wordpress 4.9 2018
$cf7 = WPCF7_ContactForm::get_current();
$submission = WPCF7_Submission::get_instance();
$data = $submission->get_posted_data();
//get posted form fields
//these are example form fields
$field1 = $data["name"];
$field2 = $data["email"];
$field3 = $data["address"];
$field4 = $data["city"];
$field5 = $data["state"];
$field6 = $data["zip"];
$field7 = $data["phone"];
//insert into external db
$mydb->insert(
//name of external db table
'table_name',
//name of table columns and which fields to insert
//these are example fields
array(
'name' => $field1,
'email' => $field2,
'address' => $field3,
'city' => $field4,
'state' => $field5,
'zip' => $field6,
'phone' => $field7
),
//field formats: %s = string, %d = integer, %f = float
array(
'%s','%s','%s','%s','%s','%s','%s'
)
);
}
}
}
add_action("wpcf7_before_send_mail", "wpcf7_send_to_external");
