mage-eventpress/inc/mep_csv_export.php

<?php
add_action( 'admin_notices', 'export_btn' );
function export_btn() {
    global $typenow;
    if ($typenow == 'mep_events_attendees') {
        ?>
        <div class="wrap alignright">
            <form method='get' action="edit.php">
                <input type="hidden" name='post_type' value="mep_events_attendees"/>
                <input type="hidden" name='noheader' value="1"/>
                <?php 
                  if ( isset( $_GET['meta_value'] )) {
                ?>
              <input type="hidden" name='meta_value' value="<?php echo $_GET['meta_value']; ?>"/>
              <?php } ?>                
              <input type="hidden" name='action' value="download_csv"/>
                <input type="submit" name='export' id="csvExport" value="<?php _e('Export to CSV','mage-eventpress'); ?>"/>
            </form>
        </div>

        <?php
    }
}


function mep_get_event_user_fields($post_id){
      $row = array(
        'Order ID',
        'Event',        
        'Ticket',                
        'Full Name',
        'Email',
        'Phone',
        'Addresss',
        'Tee Size'
    );
$crow = array();
$mep_form_builder_data = get_post_meta($post_id, 'mep_form_builder_data', true);
  if ( $mep_form_builder_data ) {
    foreach ( $mep_form_builder_data as $_field ) {
      $crow[] = $_field['mep_fbc_label'];
    }
  }
return array_merge($row, $crow);
}



function mep_get_event_user_fields_data($post_id,$event){
$values = get_post_custom( $post_id );
      $row = array(
            get_post_meta( $post_id, 'ea_order_id', true ),
            get_post_meta( $post_id, 'ea_event_name', true ),  
            get_post_meta( $post_id, 'ea_ticket_type', true ),                      
            get_post_meta( $post_id, 'ea_name', true ),
            get_post_meta( $post_id, 'ea_email', true ),
            get_post_meta( $post_id, 'ea_phone', true ),
            get_post_meta( $post_id, 'ea_address_1', true ),
            get_post_meta( $post_id, 'ea_tshirtsize', true )
        );
    $crow = array();
    $mep_form_builder_data = get_post_meta($event, 'mep_form_builder_data', true);
    if ( $mep_form_builder_data ) {
    foreach ( $mep_form_builder_data as $_field ) {
      $vname = "ea_".$_field['mep_fbc_id'];
      if(array_key_exists($vname, $values)){
      $crow[] =  get_post_meta( $post_id, $vname , true );
    }
    }
  }
return array_merge($row, $crow);
}





// Add action hook only if action=download_csv
if ( isset($_GET['action'] ) && $_GET['action'] == 'download_csv' )  {
  // Handle CSV Export
  add_action( 'admin_init', 'csv_export') ;
}
function csv_export() {
    // Check for current user privileges 
    if( !current_user_can( 'manage_options' ) ){ return false; }
    // Check if we are in WP-Admin
    if( !is_admin() ){ return false; }
    // Nonce Check
    // $nonce = isset( $_GET['_wpnonce'] ) ? $_GET['_wpnonce'] : '';
    // if ( ! wp_verify_nonce( $nonce, 'download_csv' ) ) {
    //     die( 'Security check error' );
    // }
    ob_start();
    $domain = $_SERVER['SERVER_NAME'];
    $filename = 'Event_Manager_Export_' . $domain . '_' . time() . '.csv';
    

        if(isset($_GET['meta_value'])){
          $post_id  = strip_tags($_GET['meta_value']);
          $header_row      = mep_get_event_user_fields($post_id);          
        }else{
        $header_row = array(
        'Order ID',
        'Event',        
        'Ticket',                
        'Full Name',
        'Email',
        'Phone',
        'Addresss',
        'Tee Size'
        );         
        }





    $data_rows = array();
    global $wpdb;

if(isset($_GET['meta_value'])){
$meta = $_GET['meta_value'];
  $query = "SELECT post_id
        FROM {$wpdb->prefix}postmeta
        WHERE meta_value = $meta
        ORDER BY meta_id ASC";
}else{
  $query = "SELECT ID
        FROM {$wpdb->prefix}posts
        WHERE post_type ='mep_events_attendees'
        ORDER BY ID ASC";
}

    $posts   = $wpdb->get_results($query);
     foreach ( $posts as $i=>$post ) {

        if(isset($_GET['meta_value'])){
          $post_id  = $post->post_id;
          $event    = strip_tags($_GET['meta_value']);
          $row      = mep_get_event_user_fields_data($post_id,$event);          
        }else{
          $post_id = $post->ID;
        $row = array(
            get_post_meta( $post_id, 'ea_order_id', true ),
            get_post_meta( $post_id, 'ea_event_name', true ),  
            get_post_meta( $post_id, 'ea_ticket_type', true ),                      
            get_post_meta( $post_id, 'ea_name', true ),
            get_post_meta( $post_id, 'ea_email', true ),
            get_post_meta( $post_id, 'ea_phone', true ),
            get_post_meta( $post_id, 'ea_address_1', true ),
            get_post_meta( $post_id, 'ea_tshirtsize', true )

        );          
        }


        $data_rows[] = $row;
    }
    $fh = @fopen( 'php://output', 'w' );
    fprintf( $fh, chr(0xEF) . chr(0xBB) . chr(0xBF) );
    header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0' );
    header( 'Content-Description: File Transfer' );
    header( 'Content-type: text/csv' );
    header( "Content-Disposition: attachment; filename={$filename}" );
    header( 'Expires: 0' );
    header( 'Pragma: public' );
    fputcsv( $fh, $header_row );
    foreach ( $data_rows as $data_row ) {
        fputcsv( $fh, $data_row );
    }
    fclose( $fh );
    
    ob_end_flush();
    
    die();
}