WordPress database table import/export (as CSV)

wp-db-table-import-export.php

<?php
/**
 * Plugin Name: Table Import/Export
 * Description: For internal use only. To access, WP-Admin > Tools > Table Import/Export.
 */
function table_import_export_menu(){
    add_submenu_page(
        'tools.php',
        'Table Import/Export',
        'Table Import/Export',
        'manage_options',
        'table-import-export',
        'table_import_export_page',
        20
    );
}
add_action( 'admin_menu', 'table_import_export_menu' );

function get_tables(){
    global $wpdb;
    $tables = $wpdb->get_results( "SHOW TABLES", ARRAY_N );
    $table_list = array();
    foreach( $tables as $table ) {
        $table_list[] = $table[0];
    }
    return $table_list;
}

function export_table( $table_name ){
    global $wpdb;
    $results = $wpdb->get_results( "SELECT * FROM $table_name" );
    $temp_file = fopen( 'php://output', 'w' );
    $headings = array_keys( get_object_vars( $results[0] ) );
    fputcsv($temp_file, $headings);
    foreach( $results as $row ){
        fputcsv( $temp_file, (array)$row );
    }
    fclose( $temp_file );
}

function import_csv( $table_name, $file ){
    global $wpdb;
    $skipped_rows = array();
    $temp_file = fopen( $file, 'r' );
    $headers = fgetcsv( $temp_file );
    while( ( $row = fgetcsv( $temp_file ) ) !== FALSE ){
        $data = array();
        foreach( $headers as $key => $header ){
            $data[$header] = $row[$key];
        }
        $id = $data['id'];
        if( $wpdb->get_row( "SELECT * FROM $table_name WHERE id = '$id'" ) ){
            $wpdb->update( $table_name, $data, array( 'id' => $id ) );
        } else {
            $skipped_rows[] = $row;
        }
    }
    fclose( $temp_file );
    return $skipped_rows;
}

// Admin page callback function
function table_import_export_page(){
    global $wpdb;
    if( isset($_POST['export_table'] ) ){
        $table_name = $_POST['export_table'];
        header( 'Content-Type: text/csv' );
        header( 'Content-Disposition: attachment; filename="'. $table_name. '.csv"' );
        ob_end_clean(); // so we don't get WP_head() and other stuff
        export_table( $table_name );
        exit; // prevents anything more being added after the data
    } elseif( isset( $_FILES['import_file'] ) && $_FILES['import_file']['error'] == 0 ){
        $table_name = $_POST['import_table'];
        $skipped_rows = import_csv( $table_name, $_FILES['import_file']['tmp_name'] );
       ?>
        <div class="updated">
            <p>Import successful! The following rows were skipped because a matching ID for them does not exist within the database and this function does not support the addition of new data.</p>
            <ul>
                <?php foreach( $skipped_rows as $row ): ?>
                    <li><?php echo implode( ', ', $row );?></li>
                <?php endforeach; ?>
            </ul>
        </div>
        <?php
    }
   ?>
    <div class="wrap">
        <h1>Table Import/Export</h1>
        <h2>Export Table</h2>
        <form method="post">
            <select id="export_table" name="export_table">
                <?php foreach( get_tables() as $table ): ?>
                    <option value="<?php echo $table; ?>"><?php echo $table; ?></option>
                <?php endforeach; ?>
            </select>
            <input type="submit" value="Export" />
        </form>
        <h2>Import CSV File</h2>
        <form method="post" enctype="multipart/form-data">
            <select id="import_table" name="import_table">
                <?php foreach( get_tables() as $table ): ?>
                    <option value="<?php echo $table; ?>"><?php echo $table; ?></option>
                <?php endforeach; ?>
            </select>
            <input type="file" name="import_file" />
            <input type="submit" value="Import" />
        </form>
        <script>
            // attempt to ensure the table names align for them by making it so when one's updated the other changes too
            document.getElementById('export_table').addEventListener('change', function() {
                document.getElementById('import_table').value = this.value;
            });


            document.getElementById('import_table').addEventListener('change', function() {
                document.getElementById('export_table').value = this.value;
            });
        </script>
        <p style="padding: 10px; border: 2px dashed red;">Note: When importing ensure that you have selected the correct table from the dropdown. At time of export the file name was the table's name.</p>
    </div>
    <?php
}