2个结果匹配时内部服务器错误ajax搜索

Hi have an ajax search with php, jquery and ajax that searchs in the db the name and description in the articles table. When the string matchs only with one result, it's works fine, but if there are 2 results that matchs, it shows Internal server error. You can see here (http://en.organizing-erasmus.es/events/), try to write "tr" in the search and try to write "ju" (with this string there are two results that matchs, so it's shows 500 server error in the chrome console.

Search.php code:

    <?php
/************************************************
    The Search PHP File
************************************************/

require('classes/Article.php');

/************************************************
    MySQL Connect
************************************************/

// Credentials
$dbhost = "localhost";
$dbname = "hidden";
$dbuser = "hidden";
$dbpass = "hidden";

//  Connection
global $tutorial_db;

$tutorial_db = new mysqli();
$tutorial_db->connect($dbhost, $dbuser, $dbpass, $dbname);
$tutorial_db->set_charset("utf8");

//  Check Connection
if ($tutorial_db->connect_errno) {
    printf("Connect failed: %s
", $tutorial_db->connect_error);
    exit();
}

/************************************************
    Search Functionality
************************************************/

// Define Output HTML Formating
$html = '';
$html .= '<li class="result">';
$html .= '<a href="urlString">';
$html .= '<h4>nameString</h4>';
$html .= '<p>functionString</p>';
$html .= '</a>';
$html .= '</li>';

// Get Search
$search_string = preg_replace("/[^A-Za-z0-9]/", " ", $_POST['query']);
$search_string = $tutorial_db->real_escape_string($search_string);

// Check Length More Than One Character
if (strlen($search_string) >= 1 && $search_string !== ' ') {
    // Build Query
    $query = 'SELECT * FROM articles WHERE title_eng LIKE "%'.$search_string.'%" OR summary_eng LIKE "%'.$search_string.'%" OR content_eng LIKE "%'.$search_string.'%"';

    // Do Search
    $result = $tutorial_db->query($query);
    while($results = $result->fetch_array()) {
        $result_array[] = $results;
    }

    // Check If We Have Results
    if (isset($result_array)) {
        foreach ($result_array as $result) {
            function limpiarCaracteresEspeciales($string ){
     $string = htmlentities($string); 
     $string = str_replace(' ', '-', $string);
     $string = preg_replace('/\&(.)[^;]*;/', '\\1', $string); 
     return $string; 
}
$id_s = htmlspecialchars( $result['id'] );
    $titulo = htmlspecialchars( $result['title_eng'] );
           $title_url = limpiarCaracteresEspeciales($titulo);


            // Format Output Strings And Hightlight Matches
            $display_function = preg_replace("/".$search_string."/i", "<b class='highlight'>".$search_string."</b>", $result['summary_eng']);
            $display_name = preg_replace("/".$search_string."/i", "<b class='highlight'>".$search_string."</b>", $result['title_eng']);
            $eve = 'events';
            $display_url = '/'.$eve.'/'.$title_url.'/'.$id_s.'/';

            // Insert Name
            $output = str_replace('nameString', $display_name, $html);

            // Insert Function
            $output = str_replace('functionString', $display_function, $output);

            // Insert URL
            $output = str_replace('urlString', $display_url, $output);

            // Output
            echo($output);
        }
    }else{

        // Format No Results Output
        $output = str_replace('urlString', 'javascript:void(0);', $html);
        $output = str_replace('nameString', '<b>No he encontrado nada.</b>', $output);
        $output = str_replace('functionString', 'Lo siento, no me pegues plis :(', $output);

        // Output
        echo($output);
    }
}


/*
// Build Function List (Insert All Functions Into DB - From PHP)

// Compile Functions Array
$functions = get_defined_functions();
$functions = $functions['internal'];

// Loop, Format and Insert
foreach ($functions as $function) {
    $function_name = str_replace("_", " ", $function);
    $function_name = ucwords($function_name);

    $query = '';
    $query = 'INSERT INTO search SET id = "", function = "'.$function.'", name = "'.$function_name.'"';

    $tutorial_db->query($query);
}
*/
?>

custom.js (JQuery code)

/* JS File */

// Start Ready
$(document).ready(function() {  

    // Icon Click Focus
    $('.buscar-icon').click(function(){
        $('input#search').focus();
    });

    // Live Search
    // On Search Submit and Get Results
    function search() {
        var query_value = $('input#search').val();
        $('b#search-string').text(query_value);
        if(query_value !== ''){
            $.ajax({
                type: "POST",
                url: "search.php",
                data: { query: query_value },
                cache: false,
                success: function(html){
                    $("ul#results").html(html);
                }
            });
        }return false;    
    }

    $("input#search").on("keyup", function(e) {
        // Set Timeout
        clearTimeout($.data(this, 'timer'));

        // Set Search String
        var search_string = $(this).val();

        // Do Search
        if (search_string == '') {
            $("ul#results").fadeOut();
            $('p#results-text').fadeOut();
        }else{
            $("ul#results").fadeIn();
            $('p#results-text').fadeIn();
            $(this).data('timer', setTimeout(search, 100));
        };
    });


});


$("input#search").on("keydown", function(e) {
        var $listItems = $('ul#results li');
        var $listItemsa = $('ul#results li a');

             var key = e.keyCode,
        $selected = $listItems.filter('.selected'),
        $current;

    if ( key != 40 && key != 38 ) return;

    $listItems.removeClass('selected');

    if ( key == 40 ) // Down key
    {
        if ( ! $selected.length || $selected.is(':last-child') ) {
            $current = $listItems.eq(0);
        }
        else {
            $current = $selected.next();
        }
    }
    else if ( key == 38 ) // Up key
    {
        if ( ! $selected.length || $selected.is(':first-child') ) {
            $current = $listItems.last();
        }
        else {
            $current = $selected.prev();
        }
    }
    $.fn.focusWithoutScrolling = function(){
var x = $(document).scrollLeft(), y = $(document).scrollTop();
  this.focus();
  window.scrollTo(x, y);
  return this; //chainability

};
var $currenta = $current.children();
$currenta.focusWithoutScrolling();
    $current.addClass('selected');
    event.preventDefault();
        });

Markup:

    <div id="main">
<!-- Main Input -->
<input type="text" id="search" autocomplete="off">
<i class="fa fa-search fa-2x buscar-icon"></i>

<!-- Show Results -->
<ul id="results"></ul>