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Hi I'm trying to convert from a "example" wp_list_table that displays an array of data on the same page, to a "real life" table the pulls data from the database. I have the code setup to where I just need to add the DB query to make it work.

I just don't know how to query the database and make it display correctly. Would someone be willing to look at the code below and tell me how to make a query to the "links" database table in wordpress? I was thinking the query below would work, but I don't think it jives with my "example" table row and columns.

$sql = "SELECT * FROM links"; 
$data = $wpdb->get_results($sql);  

In the code below, scrolling down about 3/4 ($data = $this->example_data;), you will see the area where it would create a database query if this were a working piece of code.

Here's my functions.php file.

<?php

/* == NOTICE ===================================================================
 * Please do not alter this file. Instead: make a copy of the entire plugin, 
 * rename it, and work inside the copy. If you modify this plugin directly and 
 * an update is released, your changes will be lost!
 * ========================================================================== */



/*************************** LOAD THE BASE CLASS *******************************
 *******************************************************************************
 * The WP_List_Table class isn't automatically available to plugins, so we need
 * to check if it's available and load it if necessary.
 */
if(!class_exists('WP_List_Table')){
require_once( ABSPATH . 'wp-admin/includes/class-wp-list-table.php' );
}




/************************** CREATE A PACKAGE CLASS *****************************
 *******************************************************************************
 * Create a new list table package that extends the core WP_List_Table class.
* WP_List_Table contains most of the framework for generating the table, but we
* need to define and override some methods so that our data can be displayed
* exactly the way we need it to be.
 *   
* To display this example on a page, you will first need to instantiate the class,
* then call $yourInstance->prepare_items() to handle any data manipulation, then
* finally call $yourInstance->display() to render the table to the page.
* 
* Our theme for this list table is going to be movies.
*/
class TT_Example_List_Table extends WP_List_Table {

/** ************************************************************************
 * Normally we would be querying data from a database and manipulating that
 * for use in your list table. For this example, we're going to simplify it
 * slightly and create a pre-built array. Think of this as the data that might
 * be returned by $wpdb->query().
 * 
 * @var array 
 **************************************************************************/
var $example_data = array(
        array(
            'ID'        => 1,
            'title'     => '300',
            'rating'    => 'R',
            'director'  => 'Zach Snyder'
        ),
        array(
            'ID'        => 2,
            'title'     => 'Eyes Wide Shut',
            'rating'    => 'R',
            'director'  => 'Stanley Kubrick'
        ),
        array(
            'ID'        => 3,
            'title'     => 'Moulin Rouge!',
            'rating'    => 'PG-13',
            'director'  => 'Baz Luhrman'
        ),
        array(
            'ID'        => 4,
            'title'     => 'Snow White',
            'rating'    => 'G',
            'director'  => 'Walt Disney'
        ),
        array(
            'ID'        => 5,
            'title'     => 'Super 8',
            'rating'    => 'PG-13',
            'director'  => 'JJ Abrams'
        ),
        array(
            'ID'        => 6,
            'title'     => 'The Fountain',
            'rating'    => 'PG-13',
            'director'  => 'Darren Aronofsky'
        ),
        array(
            'ID'        => 7,
            'title'     => 'Watchmen',
            'rating'    => 'R',
            'director'  => 'Zach Snyder'
        )
    );

/** ************************************************************************
 * REQUIRED. Set up a constructor that references the parent constructor. We 
 * use the parent reference to set some default configs.
 ***************************************************************************/
function __construct(){
    global $status, $page;

    //Set parent defaults
    parent::__construct( array(
        'singular'  => 'movie',     //singular name of the listed records
        'plural'    => 'movies',    //plural name of the listed records
        'ajax'      => false        //does this table support ajax?
    ) );

}


/** ************************************************************************
 * Recommended. This method is called when the parent class can't find a method
 * specifically build for a given column. Generally, it's recommended to include
 * one method for each column you want to render, keeping your package class
 * neat and organized. For example, if the class needs to process a column
 * named 'title', it would first see if a method named $this->column_title() 
 * exists - if it does, that method will be used. If it doesn't, this one will
 * be used. Generally, you should try to use custom column methods as much as 
 * possible. 
 * 
 * Since we have defined a column_title() method later on, this method doesn't
 * need to concern itself with any column with a name of 'title'. Instead, it
 * needs to handle everything else.
 * 
 * For more detailed insight into how columns are handled, take a look at 
 * WP_List_Table::single_row_columns()
 * 
 * @param array $item A singular item (one full row's worth of data)
 * @param array $column_name The name/slug of the column to be processed
 * @return string Text or HTML to be placed inside the column <td>
 **************************************************************************/
function column_default($item, $column_name){
    switch($column_name){
        case 'rating':
        case 'director':
            return $item[$column_name];
        default:
            return print_r($item,true); //Show the whole array for troubleshooting purposes
    }
}


/** ************************************************************************
 * Recommended. This is a custom column method and is responsible for what
 * is rendered in any column with a name/slug of 'title'. Every time the class
 * needs to render a column, it first looks for a method named 
 * column_{$column_title} - if it exists, that method is run. If it doesn't
 * exist, column_default() is called instead.
 * 
 * This example also illustrates how to implement rollover actions. Actions
 * should be an associative array formatted as 'slug'=>'link html' - and you
 * will need to generate the URLs yourself. You could even ensure the links
 * 
 * 
 * @see WP_List_Table::::single_row_columns()
 * @param array $item A singular item (one full row's worth of data)
 * @return string Text to be placed inside the column <td> (movie title only)
 **************************************************************************/
function column_title($item){

    //Build row actions
    $actions = array(
        'edit'      => sprintf('<a href="?page=%s&action=%s&movie=%s">Edit</a>',$_REQUEST['page'],'edit',$item['ID']),
        'delete'    => sprintf('<a href="?page=%s&action=%s&movie=%s">Delete</a>',$_REQUEST['page'],'delete',$item['ID']),
    );

    //Return the title contents
   return sprintf('<a href="#"><b>%1$s</b></a> %3$s',
        /*$1%s*/ $item['title'],
        /*$2%s*/ $item['ID'],
        /*$3%s*/ $this->row_actions($actions)
    );
}

/** ************************************************************************
 * REQUIRED if displaying checkboxes or using bulk actions! The 'cb' column
 * is given special treatment when columns are processed. It ALWAYS needs to
 * have it's own method.
 * 
 * @see WP_List_Table::::single_row_columns()
 * @param array $item A singular item (one full row's worth of data)
 * @return string Text to be placed inside the column <td> (movie title only)
 **************************************************************************/
function column_cb($item){
    return sprintf(
        '<input type="checkbox" name="%1$s[]" value="%2$s" />',
        /*$1%s*/ $this->_args['singular'],  //Let's simply repurpose the table's singular label ("movie")
        /*$2%s*/ $item['ID']                //The value of the checkbox should be the record's id
    );
}


/** ************************************************************************
 * REQUIRED! This method dictates the table's columns and titles. This should
 * return an array where the key is the column slug (and class) and the value 
 * is the column's title text. If you need a checkbox for bulk actions, refer
 * to the $columns array below.
 * 
 * The 'cb' column is treated differently than the rest. If including a checkbox
 * column in your table you must create a column_cb() method. If you don't need
 * bulk actions or checkboxes, simply leave the 'cb' entry out of your array.
 * 
 * @see WP_List_Table::::single_row_columns()
 * @return array An associative array containing column information: 'slugs'=>'Visible Titles'
 **************************************************************************/
function get_columns(){
    $columns = array(
        'cb'        => '<input type="checkbox" />', //Render a checkbox instead of text
        'title'     => 'Custom Widget Name',
        'rating'    => 'Rating',
        'director'  => 'Director'
    );
    return $columns;
}

/** ************************************************************************
 * Optional. If you want one or more columns to be sortable (ASC/DESC toggle), 
 * you will need to register it here. This should return an array where the 
 * key is the column that needs to be sortable, and the value is db column to 
 * sort by. Often, the key and value will be the same, but this is not always
 * the case (as the value is a column name from the database, not the list table).
 * 
 * This method merely defines which columns should be sortable and makes them
 * clickable - it does not handle the actual sorting. You still need to detect
 * the ORDERBY and ORDER querystring variables within prepare_items() and sort
 * your data accordingly (usually by modifying your query).
 * 
 * @return array An associative array containing all the columns that should be sortable: 'slugs'=>array('data_values',bool)
 **************************************************************************/
function get_sortable_columns() {
    $sortable_columns = array(
        'title'     => array('title',true),     //true means its already sorted
        'rating'    => array('rating',false),
        'director'  => array('director',false)
    );
    return $sortable_columns;
}


/** ************************************************************************
 * Optional. If you need to include bulk actions in your list table, this is
 * the place to define them. Bulk actions are an associative array in the format
 * 'slug'=>'Visible Title'
 * 
 * If this method returns an empty value, no bulk action will be rendered. If
 * you specify any bulk actions, the bulk actions box will be rendered with
 * the table automatically on display().
 * 
 * Also note that list tables are not automatically wrapped in <form> elements,
 * so you will need to create those manually in order for bulk actions to function.
 * 
 * @return array An associative array containing all the bulk actions: 'slugs'=>'Visible Titles'
 **************************************************************************/
function get_bulk_actions() {
    $actions = array(
        'delete'    => 'Delete'
    );
    return $actions;
}


/** ************************************************************************
 * Optional. You can handle your bulk actions anywhere or anyhow you prefer.
 * For this example package, we will handle it in the class to keep things
 * clean and organized.
 * 
 * @see $this->prepare_items()
 **************************************************************************/
function process_bulk_action() {

    //Detect when a bulk action is being triggered...
    if( 'delete'===$this->current_action() ) {
        wp_die('Items deleted (or they would be if we had items to delete)!');
    }

}


/** ************************************************************************
 * REQUIRED! This is where you prepare your data for display. This method will
 * usually be used to query the database, sort and filter the data, and generally
 * get it ready to be displayed. At a minimum, we should set $this->items and
 * $this->set_pagination_args(), although the following properties and methods
 * are frequently interacted with here...
 * 
 * @uses $this->_column_headers
 * @uses $this->items
 * @uses $this->get_columns()
 * @uses $this->get_sortable_columns()
 * @uses $this->get_pagenum()
 * @uses $this->set_pagination_args()
 **************************************************************************/
function prepare_items() {

    /**
     * First, lets decide how many records per page to show
     */
    $per_page = 5;


    /**
     * REQUIRED. Now we need to define our column headers. This includes a complete
     * array of columns to be displayed (slugs & titles), a list of columns
     * to keep hidden, and a list of columns that are sortable. Each of these
     * can be defined in another method (as we've done here) before being
     * used to build the value for our _column_headers property.
     */
    $columns = $this->get_columns();
    $hidden = array();
    $sortable = $this->get_sortable_columns();


    /**
     * REQUIRED. Finally, we build an array to be used by the class for column 
     * headers. The $this->_column_headers property takes an array which contains
     * 3 other arrays. One for all columns, one for hidden columns, and one
     * for sortable columns.
     */
    $this->_column_headers = array($columns, $hidden, $sortable);


    /**
     * Optional. You can handle your bulk actions however you see fit. In this
     * case, we'll handle them within our package just to keep things clean.
     */
    $this->process_bulk_action();


    /**
     * Instead of querying a database, we're going to fetch the example data
     * property we created for use in this plugin. This makes this example 
     * package slightly different than one you might build on your own. In 
     * this example, we'll be using array manipulation to sort and paginate 
     * our data. In a real-world implementation, you will probably want to 
     * use sort and pagination data to build a custom query instead, as you'll
     * be able to use your precisely-queried data immediately.
     */
   $data = $this->example_data;




    /**
     * This checks for sorting input and sorts the data in our array accordingly.
     * 
     * In a real-world situation involving a database, you would probably want 
     * to handle sorting by passing the 'orderby' and 'order' values directly 
     * to a custom query. The returned data will be pre-sorted, and this array
     * sorting technique would be unnecessary.
     */
    function usort_reorder($a,$b){
        $orderby = (!empty($_REQUEST['orderby'])) ? $_REQUEST['orderby'] : 'title'; //If no sort, default to title
        $order = (!empty($_REQUEST['order'])) ? $_REQUEST['order'] : 'asc'; //If no order, default to asc
        $result = strcmp($a[$orderby], $b[$orderby]); //Determine sort order
        return ($order==='asc') ? $result : -$result; //Send final sort direction to usort

    usort($data, 'usort_reorder');

}














































    /**
     * REQUIRED for pagination. Let's figure out what page the user is currently 
     * looking at. We'll need this later, so you should always include it in 
     * your own package classes.
     */
    $current_page = $this->get_pagenum();

    /**
     * REQUIRED for pagination. Let's check how many items are in our data array. 
     * In real-world use, this would be the total number of items in your database, 
     * without filtering. We'll need this later, so you should always include it 
     * in your own package classes.
     */
    $total_items = count($data);


    /**
     * The WP_List_Table class does not handle pagination for us, so we need
     * to ensure that the data is trimmed to only the current page. We can use
     * array_slice() to 
     */
    $data = array_slice($data,(($current_page-1)*$per_page),$per_page);



    /**
     * REQUIRED. Now we can add our *sorted* data to the items property, where 
     * it can be used by the rest of the class.
     */
    $this->items = $data;


    /**
     * REQUIRED. We also have to register our pagination options & calculations.
     */
    $this->set_pagination_args( array(
        'total_items' => $total_items,                  //WE have to calculate the total number of items
        'per_page'    => $per_page,                     //WE have to determine how many items to show on a page
        'total_pages' => ceil($total_items/$per_page)   //WE have to calculate the total number of pages
    ) );
}

}





/** ************************ REGISTER THE TEST PAGE ****************************
 *******************************************************************************
 * Now we just need to define an admin page. For this example, we'll add a top-level
 * menu item to the bottom of the admin menus.
 */
function tt_add_menu_items(){
add_menu_page('Custom Widgets', 'Custom Widgets', 'activate_plugins', 'tt_list_test', 'tt_render_list_page');
} add_action('admin_menu', 'tt_add_menu_items');


/***************************** RENDER TEST PAGE ********************************
 *******************************************************************************
 * This function renders the admin page and the example list table. Although it's
 * possible to call prepare_items() and display() from the constructor, there
 * are often times where you may need to include logic here between those steps,
 * so we've instead called those methods explicitly. It keeps things flexible, and
 * it's the way the list tables are used in the WordPress core.
 */
function tt_render_list_page(){

//Create an instance of our package class...
$testListTable = new TT_Example_List_Table();
//Fetch, prepare, sort, and filter our data...
$testListTable->prepare_items();

?>
<div class="wrap" style="width:70%">

    <div id="icon-themes" class="icon32"><br/></div>
    <h2>Custom Widgets</h2>
    <?php

$active_tab = isset( $_GET[ 'tab' ] ) ? $_GET[ 'tab' ] : 'custom_widget_manager';

?>


    <h2 class="nav-tab-wrapper">
       <a href="?page=tt_list_test&tab=custom_widget_manager" class="nav-tab <?php echo $active_tab == 'custom_widget_manager' ? 'nav-tab-active' : ''; ?>">Custom Widget Manager</a>
       <a href="?page=tt_list_test&tab=add_custom_widget" class="nav-tab <?php echo $active_tab == 'add_custom_widget' ? 'nav-tab-active' : ''; ?>">Add Custom Widget</a>
        </h2>

   <!-- Forms are NOT created automatically, so you need to wrap the table in one to use features like bulk actions -->
    <form id="movies-filter" method="get">
        <!-- For plugins, we also need to ensure that the form posts back to our current page -->
        <input type="hidden" name="page" value="<?php echo $_REQUEST['page'] ?>" />
        <!-- Now we can render the completed list table -->

        <?php $testListTable->display(); ?>

    </form>

</div>
<?php
}
share|improve this question

1 Answer 1

up vote 1 down vote accepted

WordPress adds prefixes to tables names, which was setup on installation. So by default there is wp_ prefix for tables names. It means that by default table name for links will be wp_links. But you shouldn't care about standard tables name, because all of them exists as parameters of wpdb class (read Table section), so your query should be built like this:

$sql = "SELECT * FROM " . $wpdb->links; 
$data = $wpdb->get_results($sql);
share|improve this answer
    
Thanks, Eugene.....your explanation was informative. –  Rob Myrick Jun 6 '12 at 16:01

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