Include custom field data from donor metadata in GiveWP's donation history export

givewp-export-donor-custom-field-data.php

<?php

/**
* This function sets the column header in the generated CSV file for the custom field. Add an if statement for each aditional field.
*/
function givewp_custom_columns_name( $cols ) {
	if ( isset( $cols['givewp_employer'] ) ) {
		$cols['givewp_employer'] = __( 'Employer', 'give' );
	}

	return $cols;

}
add_filter( 'give_export_donation_get_columns_name', 'givewp_custom_columns_name' );

/**
* Thi function adds a checkbox to the Donor fields section in the Export page. Add an if statement for each aditional field.
*/
function givewp_export_custom_field() {
	?>
	<li>
		<label for="give-export-employer">
			<input type="checkbox" checked
			       name="give_give_donations_export_option[givewp_employer]"
			       id="give-export-employer"><?php _e( 'Employer', 'give' ); ?>
		</label>
	</li>
	<?php
}

add_action( 'give_export_donation_standard_donor_fields', 'givewp_export_custom_field' );

/**
* This function populates the CSV with the custom field data. Include additional items in the $data array as needed.
*/
use Give\Donors\Models\Donor;
function givewp_export_custom_field_data( $data, $payment, $columns, $instance ) {
	// We use the donor email to get the donor id.
  $email = $payment->get_meta( '_give_payment_donor_email' );
	$donorId = Donor::whereEmail($email)->id;
  
  // With the donor id, we can query any custom field stored in the donormeta table
  $employer = give()->donor_meta->get_meta( $donorId, 'employer' , true);
	if ( ! empty( $columns['givewp_employer'] )) {
		if (  $employer ) {
			$data['givewp_employer'] =  $employer ;
		} else {
			$data['givewp_employer'] = '';
		}
	}

	return $data;
}

add_filter( 'give_export_donation_data', 'givewp_export_custom_field_data', 20, 4 );