a basic CSV export example

csv-export-example.php

<?php
/**
 * Devin CSV Export
 *
 * Contains our export processing
 */
/*
	Copyright 2015 Reaktiv Studios

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; version 2 of the License (GPL v2) only.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

if ( ! class_exists( 'Devin_CSV_Export' ) ) {

// Start up the engine
class Devin_CSV_Export
{

	/**
	 * [__construct description]
	 */
	public function __construct() {
		add_action( 'admin_menu',                   array( $this, 'export_menu'             )           );
		add_action( 'admin_init',                   array( $this, 'export_init'             )           );
	}

	/**
	 * call the menu item to add the export page
	 *
	 * @return [type] [description]
	 */
	public function export_menu() {
		add_users_page( 'Devin CSV Export', 'Devin CSV Export', 'manage_options', 'devin-csv-export', array( __class__, 'csv_export_page' ) );
	}

	/**
	 * the actual export page
	 * @return [type] [description]
	 */
	public static function csv_export_page() {

		// wrap the form
		echo '<div class="wrap custom-sort-wrap">';

			// set the form title
			echo '<h2>' . esc_html( get_admin_page_title() ) . '</h2>';

			// begin the form portion itself
			echo '<form method="post">';

			echo wp_nonce_field( 'csv_export_nonce', 'csv_export_nonce', false, false );

			echo '<button type="submit" class="button button-primary">Export Data</button>';

			echo '<input type="hidden" name="csv-export-trigger" value="go">';

			echo '</form>';
		echo '</div>';
	}

	/**
	 * trigger our export function
	 *
	 * @return PA_Calculator_Logging
	 */
	public function export_init() {

		// bail if no access
		if ( ! current_user_can( 'manage_options' ) ) {
			return;
		}

		// bail if no page reference
		if ( empty( $_POST['csv-export-trigger'] ) || 'go' !== $_POST['csv-export-trigger'] ) {
			return;
		}

		// check nonce and bail if missing
		if ( empty( $_POST['csv_export_nonce'] ) || ! wp_verify_nonce( $_POST['csv_export_nonce'], 'csv_export_nonce' ) ) {
			return;
		}

		// fetch the user export data
		if ( false === $data = self::export_query() ) {
			return;
		}

		// run the export
		self::process_export( $data );
	}

	/**
	 * the actual export process
	 *
	 * @return
	 */
	public static function process_export( $data = array() ) {

		// build the file name
		$file   = 'devin_csv_export_' . strftime( '%Y-%m-%d' );

		header( 'Pragma: public' );
		header( 'Cache-control: max-age=0' );
		header( 'Content-Type: text/csv; charset=utf8' );
		header( 'Content-Disposition: attachment; filename=' . $file . '.csv' );

		// create the file and echo it
		echo self::csv_create( $data );

		// and bail
		exit();
	}

	/**
	 * create the CSV data
	 *
	 * @return
	 */
	public static function csv_create( $data = array(), $col_sep = ',', $row_sep = "\n", $qut = '"' ) {

		// bail with no data
		if ( empty( $data ) ) {
			return false;
		}

		// set an empty
		$build  = '';

		// add the header
		$build .= self::build_export_header();

		// Data rows
		foreach ( $data as $item ) {

			$field1 = $item['field1'];
			$field2 = $item['field2'];
			$field3 = $item['field3'];

			// set a temp
			$row    = '';

			// set columns
			$row   .= "$col_sep$qut$field1$qut";  // first field
			$row   .= "$col_sep$qut$field2$qut";  // second field
			$row   .= "$col_sep$qut$field3$qut";  // third field

			// add the field
			$build .= substr( $row, 1 ) . $row_sep;
		}

		// return the build file
		return $build;
	}

	/**
	 * Build the header row for a CSV export
	 *
	 * @return string
	 */
	public static function build_export_header() {

		// Header row
		$output = '"Field1","Field2","Field3","Field4"'."\n";

		// return the header row
		return $output;
	}

	/**
	 * fetch the students for the export
	 *
	 * @return [type] [description]
	 */
	public static function export_query() {

		// QUERY YOUR DATA HOWEVER YOU NEED TO

	}

// end class
}

// end exists check
}


// Instantiate our class
new Devin_CSV_Export();