Why does the code work under admin and not under guest?

Question

1C-Bitrix

The code

<a href="/inc/ajax/city.php" class="lightbox-inline-ajax"><?=$_SESSION['city']?><?=$cont[0]["NAME"]?></a>

city.php file

<?include($_SERVER['DOCUMENT_ROOT']."/bitrix/modules/main/include/prolog_before.php");
$template = '/bitrix/templates/main';
include($_SERVER['DOCUMENT_ROOT'].$template."/inc/functions.php");
IncludeTemplateLangFile($template.'/header.php');
CModule::IncludeModule("iblock");
CModule::IncludeModule("catalog");
CModule::IncludeModule("sale");?>


<div id="city" class="lightbox mfp-hide">
  
    <p class="h3">Выбрать город</p>
    <input type="text" class="search-city input-text selcity" placeholder="Ваш город">
    
    <div class="scroll-city load_cities">  
                                       
        <ul> 
        <small>Выберите город из списка, или начните вводить название.</small><br>
                <li><a class="" href="?city=Астрахань">Астрахань</a><br>
                <li><a class="" href="?city=Волгоград">Волгоград</a><br>
                <li><a class="" href="?city=Краснодар">Краснодар</a><br>
                <li><a class="" href="?city=Сочи">Сочи</a><br>
                <li><a class="" href="?city=Новороссийск">Новороссийск</a><br>
                <li><a class="" href="?city=Ростов-на-Дону">Ростов-на-Дону</a><br>
                <li><a class="" href="?city=Севастополь">Севастополь</a><br>
                <li><a class="" href="?city=Ставрополь">Ставрополь</a><br>
                <li><a class="" href="?city=Новороссийск">Новороссийск</a><br>

        </ul>

        <div class="clr"></div>
    </div>
</div><!--.lightbox-end-->

<script>
    $('.selcity').on('keyup', function(){
        $('.load_cities').load('/inc/ajax/cities.php', {'name':$(this).val()});
    });
</script>

cities.php file

<?include($_SERVER['DOCUMENT_ROOT']."/bitrix/modules/main/include/prolog_before.php");

CModule::IncludeModule("iblock");
CModule::IncludeModule("catalog");
CModule::IncludeModule("sale");?>
    <div class="scroll-city">                              
        <ul> 
    <?$filter = array("LID" => LANGUAGE_ID);
    $filter = array("LID" => LANGUAGE_ID);
    if($_POST['name']!='') $filter["%CITY_NAME"] = $_POST['name'];
    $db_vars = CSaleLocation::GetList(array("CITY_NAME"=>"ASC"),$filter);
    $n = 0;
    while($city = $db_vars->GetNext()):
      $n++;
        //if(!preg_match("#^".strtolower($_POST['q'])."#i",strtolower($city['CITY_NAME']))) continue;
        if(trim($city['CITY_NAME']=='')) continue;?>
         <li><a href='?city=<?=$city['CITY_NAME']?>' noindex nofollow class="unitt"><?=$city['CITY_NAME']?></a><!--li-end-->
        <?if($n>30){?>
        	<br><small>Введите больше букв, чтобы получить нужный город</small>
        	<?break;
        }?>
    <?endwhile;?>
  </ul>
    </div>

Answer 1

We look at the rights to the folder where these files are located, as well as the rights for the files themselves.
Next, we look at the rights to folders and files used in the code