Dynamic input fields in WordPress widgets

Try this code, I tested it and it works. The js code needs to be inserted in footer not in widget, otherwise the click button will be executed twice.

In the function widget(),you will see the loop to display the input values.

    <?php/*Plugin Name: Dynamic Fields WidgetDescription: Dynamic FieldsVersion: 0.0Author: Rain Man*/// Creating the widgetclass dynamic_widget extends WP_Widget{    public $courses;    public function __construct()    {        parent::__construct(          // Base ID of your widget          'dynamic_widget',          // Widget name will appear in UI          __('Dynamic Widget', 'dynamic_widget_domain'),          // Widget description          array('description' => __('Sample Dynamic Widget', 'dynamic_widget_domain'))        );        $this->courses = array(          'Chemistry'    => array(            'coursecode'   => 'Chemistry 2059',            'professor' => 'Dr. James Bond',          ),          'Biology'   => array(            'coursecode'   => 'Biology 3029',            'professor' => 'Dr. James Bond',          ),          'Math' => array(            'coursecode'   => 'Math 2043',            'professor' => 'Dr. James Bond',          ),          'Physics'  => array(            'coursecode'   => 'Physics 2075',            'professor' => 'Dr. James Bond',          )        );        add_action( 'in_admin_footer',array( $this,'jsfooter'));    }    public function jsfooter() {    ?>    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>    <script type="text/javascript">    jQuery(document).ready(function( $ ){        $(document ).off('click').on('click','div.open .add-row' , function() {        var row = $(this).closest('tr').clone(true);        row.find('input').each(function(){            $(this).val("");        });        // row.insertBefore( '#repeatable-fieldset-one tbody>tr:last' );        $(this).parents('tr').after(row);        return false;      });      $( document).on('click',  'div.open .remove-row',function() {          if ($(this).parents('tbody').find('tr').length >1) {            $(this).parents('tr').remove();         }        return false;      });    });    </script>    <?php    }// widgetpublic function widget($args, $instance){    $title = apply_filters('widget_title', $instance['title']);// This is where you run the code and display the output    foreach ($this->courses as $course_key => $course_info) {        echo $course_info['coursecode'] .'<br>';         foreach ($instance['repeat'][$course_key ]["fall"] as $k=>$field) {            echo 'Fall Term ' . $field .' / ';            echo 'Winter Term ' . $instance['repeat'][$course_key ]["winter"][$k] .'<br>';        }    }    echo $args['after_widget'];}// formpublic function form($instance){    if (isset($instance[ 'title' ])) {        $title = $instance[ 'title' ];    } else {        $title = __('New title', 'dynamic_widget_domain');    }// Widget admin form    $repeatable_fields= isset ( $instance['repeat'] ) ? $instance['repeat'] : array();     ?><?php foreach ($this->courses as $course_key => $course_info) { ?><label><?php echo $course_info['coursecode']; ?></label><table id="repeatable-fieldset-one" width="100%"><thead>  <tr>    <th width="40%">Fall Term</th>    <th width="40%">Winter Term</th>    <th width="8%"></th>    <th width="8%"></th>  </tr></thead><tbody><?phpif ($repeatable_fields[$course_key ]["fall"] || $repeatable_fields[$course_key ]["winter"]) :foreach ($repeatable_fields[$course_key ]["fall"] as $k=>$field) {    ?><tr>  <td><input type="text" class="widefat" name="<?php echo $this->get_field_name( 'repeat' )?>[<?php echo $course_key;?>][fall][]" value="<?php echo $field; ?>" /></td>  <td><input type="text" class="widefat" name="<?php echo $this->get_field_name( 'repeat' )?>[<?php echo $course_key;?>][winter][]" value="<?php echo $repeatable_fields[$course_key ]["winter"][$k]; ?>" /></td>  <td><a class="button remove-row" href="#">Remove</a></td>  <td><a class="button add-row" class="button" href="#">Add</a></td></tr><?php} else :// show a blank one?><tr>  <td><input type="text" class="widefat" name="<?php echo $this->get_field_name( 'repeat' )?>[<?php echo $course_key;?>][fall][]" /></td>  <td><input type="text" class="widefat" name="<?php echo $this->get_field_name( 'repeat' )?>[<?php echo $course_key;?>][winter][]" value="" /></td>  <td><a class="button remove-row" href="#">Remove</a></td>  <td><a class="button add-row" class="button" href="#">Add</a></td></tr><?php endif; ?></tbody></table><?php } ?><!-- empty hidden one for jQuery --><?php}// updatepublic function update($new_instance, $old_instance){    $instance = array();    $instance['title'] = (!empty($new_instance['title'])) ? strip_tags($new_instance['title']) : '';    $instance['repeat'] = array();    if ( isset ( $new_instance['repeat'] ) )    {        foreach ( $new_instance['repeat'] as $k =>$value )        {                $instance['repeat'][$k] = $value;        }    }    return $instance;}} // Class dynamic_widget ends here// Register and load the widgetfunction wpb_load_widget(){    register_widget('dynamic_widget');}add_action('widgets_init', 'wpb_load_widget');

The data will be stored in $instance['repeat"] in an array like that (to understand how I made the loop)

    array (size=4)  'Chemistry' =>     array (size=2)      'fall' =>         array (size=1)          0 => string 'AAA' (length=3)      'winter' =>         array (size=1)          0 => string 'BBBBBBB' (length=7)  'Biology' =>     array (size=2)      'fall' =>         array (size=2)          0 => string 'CCCCCC' (length=6)          1 => string 'EEEEEEE' (length=7)      'winter' =>         array (size=2)          0 => string 'DDDD' (length=4)          1 => string 'FFFFFFFF' (length=8)  'Math' =>     array (size=2)      'fall' =>         array (size=1)          0 => string 'GGGGGGG' (length=7)      'winter' =>         array (size=1)          0 => string 'HHHHHH' (length=6)  'Physics' =>     array (size=2)      'fall' =>         array (size=1)          0 => string 'IIIIIIIII' (length=9)      'winter' =>         array (size=1)          0 => string 'JJJJJJJJ' (length=8)

I think customising this plugin may serve the purpose: https://wordpress.org/plugins/advanced-custom-fields-table-field/installation/

Updated.

        <?php        /*        Plugin Name: Dynamic Fields Widget        Description: Dynamic Fields        Version: 0.0        Author: Rain Man        */        // Creating the widget        class dynamic_widget extends WP_Widget        {            public function __construct()            {                parent::__construct(                  'dynamic_widget', __('Dynamic Widget', 'dynamic_widget_domain'),                  array('description' => __('Sample Dynamic Widget', 'dynamic_widget_domain'))                );            }        // widget        public function widget($args, $instance)        {            $title = apply_filters('widget_title', $instance['title']);            // This is where you run the code and display the output            echo __('Hello, World!', 'dynamic_widget_domain');            echo $args['after_widget'];        }        // form        public function form($instance)        {            if (isset($instance[ 'title' ])) {                $title = $instance[ 'title' ];            } else {                $title = __('New title', 'dynamic_widget_domain');            }        // Widget admin form            $repeatable_fields = array();            $courses = array(              'Chemistry'    => array(                'coursecode'   => 'Chemistry 2059',                'professor' => 'Dr. James Bond',                'id' => 'test1',              ),              'Biology'   => array(                'coursecode'   => 'Biology 3029',                'professor' => 'Dr. James Bond',                    'id' => 'test2',              ),              'Math' => array(                'coursecode'   => 'Math 2043',                    'id' => 'test3',              ),              'Physics'  => array(                'coursecode'   => 'Physics 2075',                'id' => 'test4',              )            );        $Inc=1;        foreach ($courses as $course_key => $course_info) {             echo $Inc;            ?>        <label><?php echo $course_info['coursecode']; ?></label>        <table id="repeatable-fieldset-<?php echo $course_info['id']; ?>" width="100%" class="tableclass">        <thead>          <tr>            <th width="40%">Fall Term</th>            <th width="40%">Winter Term</th>            <th width="8%"></th>          </tr>        </thead>        <tbody>        <?php          if ($repeatable_fields):                foreach ($repeatable_fields as $field) {        ?>                    <tr>                      <td><input type="text" class="widefat" name="name[]" value="<?php if ($field['name'] != '') { echo esc_attr($field['name']);} ?>" /></td>                      <td></td>                      <td><input type="text" class="widefat" name="url[]" value="<?php if ($field['url'] != '') {   echo esc_attr($field['url']); } else { echo ''; } ?>" /></td>                      <td><a class="button remove-row" href="#">Remove</a></td>                      <td><a id="add-row" class="button addrowbtn" href="#">Add</a></td>                    </tr>                <?php   }         else:        // show a blank one        ?>        <tr>          <td><input type="text" class="widefat" name="name[]" /></td>          <td><input type="text" class="widefat" name="url[]" value="" /></td>          <td><a class="button remove-row" href="#">Remove</a></td>          <td><a id="add-row" class="button addrowbtn" href="#">Add</a></td>        </tr>        <tr class="tablerowclone">          <td><input type="text" class="widefat" name="name[]" /></td>          <td><input type="text" class="widefat" name="url[]" value="" /></td>          <td><a class="button remove-row" href="#">Remove</a></td>          <td><a id="add-row" class="button addrowbtn" href="#">Add</a></td>        </tr>        <?php endif; } ?>        <?  $Inc++; } ?>        </tbody>        </table>        <style>            .tablerowclone{display:none;}            </style>        </p>        <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>        <script type="text/javascript">        jQuery(document).ready(function( $ ){          jQuery(document).off().on('click',' .addrowbtn', function(event) {               event.preventDefault();            var row = jQuery(this).closest(".tableclass").find("tr:last").clone();            row.removeClass( 'tablerowclone' );            //row.insertBefore( '#repeatable-fieldset-one tbody>tr:last' );            row.insertBefore(jQuery(this).closest(".tableclass").find("tbody tr.tablerowclone"));            return false;          });          jQuery(document).on('click', '.remove-row' , function() {            var RowLenth  = jQuery(this).closest("tbody").children().length;                if(RowLenth>2){                    jQuery(this).parents('tr').remove();                                        }            return false;          });        });        </script>        <?php        }    public function update($new_instance, $old_instance){        $instance = array();        $instance['title'] = (!empty($new_instance['title'])) ? strip_tags($new_instance['title']) : '';        return $instance;    } } function wpb_load_widget() {  register_widget('dynamic_widget'); }add_action('widgets_init', 'wpb_load_widget');