Creating multilingual glossary for WP

I'm trying to create multilingual glossary using WP WPML custom post type. And I found solution to achieve this. Link to the page example - link

1) Added to functions.php

function get_ajax_url() {
    if (is_page(array(2017,2021,2023,2027)))  {
    wp_enqueue_script( 'ajax-script', get_template_directory_uri() . '/js/alphabet.js', array('jquery') );

    wp_localize_script( 'ajax-script', 'my_ajax_object',
            array( 'ajax_url' = admin_url( 'admin-ajax.php' ) ) );
    }
}
add_action( 'wp_enqueue_scripts', 'get_ajax_url' );

alphabet.js file contains this script:

jQuery(document).ready(function($) 
  {
    jQuery('.alphabet').click(function(){
      var data = {
        action: 'get_by_char',
        char: this.id
      };

      jQuery.post(my_ajax_object.ajaxurl, data, function(response) {

        $("#abc-drugs").html('');

        $.each($.parseJSON(response), function() {
          var they = this;

            $("#abc-drugs").append
            (
              'li class="drug"' + 
                'a href="' + they.url + '"' +
                  'h2 class="md7_drug_title"' + they.title + '/h2' + 
                '/a' +
               '/li'
            );
        });

          if(response.length  3){
          $("#abc-drugs").html('div class="no-drug-array"Препаратов не найдено/div');
          };

      });
    })
  });

Then I have added this to functions.php

function get_by_char_callback() 
{    
    global $wpdb;
    $b=array();
    $char=$_POST['char'];

    $a=$wpdb-get_results('SELECT post_title,ID FROM wpwv_posts where post_type="drug" and post_status="publish"  and (post_title like "[:ru]'.$char.'%" or post_title like "%[:en]'.$char.'%" or post_title like "'.$char.'%") ',ARRAY_A  );       

    foreach ($a as $key = $value) 
    {       

        $b[$key]['title']=translate($value['post_title']);
    }
    echo json_encode($b);
    wp_die(); 
}

add_action('wp_ajax_get_by_char', 'get_by_char_callback');
add_action('wp_ajax_nopriv_get_by_char', 'get_by_char_callback');

And my page template contains this code:

div class="alphabet-wrap"
                  ?php 
                    $alphabet=array(
                            'ru_RU'=array('а','б','в','г','д','е','ё','ж','з','и','й','к','л','м','н','о','п','р','с','т','у','ф','х','ц','ч','ш','щ','э','ю','я'),
                            'en_US'=array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'),
                            'de_DE'=array('a','ä','b','c','d','e','f','g','h','i','j','k','l','m','n','o','ö','p','q','r','s','ß','t','u','ü','v','w','x','y','z'),

                          );
                    foreach ($alphabet[get_locale()] as $key = $value):
                  ?
                  span id="?=$value?" class="alphabet"?=$value?/span
                  ?php endforeach;?
                /div


                  ul class="drugs" id="abc-drugs"
                    ?php $args = array(
                        'post_type' = 'drug',
                        'posts_per_page' = -1
                        );
                      $loop = new WP_Query( $args );
                      if ( $loop-have_posts() ) {
                        while ( $loop-have_posts() ) : $loop-the_post(); ?
                          a href="?php the_permalink() ?"?php the_title() ?/a
                        ?php endwhile;
                      } else {
                        echo __( 'Препаратов не найдено' );
                      }
                      wp_reset_postdata();
                    ?
                  /ul

And when I debug this page (click on any letter) I see the error in console

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

Where I was mistaken? Thanks in advance)