Error making request without refresh in database

Question

Guys, I’m making a system that when searching the name of an access in the search field, it searches in the database some word referring to what the user wrote in the input... I followed a youtube tutorial to do because what I wanted.

Javascript code at the end of index.php

                <form method="post">
                    <div class="input-field col s12 l12">
                        <input id="pesquisa" name="pesquisa" type="text">
                        <label for="pesquisa">Pesquisar Acesso...</label>
                    </div>
                </form>

<script>
    $("#pesquisa").keyup(function(){
    var busca = $("#pesquisa").val();

    $.post('pesquisaAcesso.php', {busca: busca},function(data){
      $("#result").html(data);
    });
  });

</script>

Code of the searchAccess.php

Pastebin.com/Fnji0tlx

placed in Pastebin because here the code . php is not indented

Anyway, when I try to search the name of the access in the field, it returns me the following error. It is not taking the data passed via post, if I modify the variable for an access you have in the bank, it searches normal, but in $_POST it does not take the value that is placed in the input.