title: Passing data via Modal Bootstrap and getting php variable?
body: <p>I'm trying to get an input value passed via jquery and setting into a php variable, but I don't know how to do that.</p>
  
  <p><strong>This button have the value that I want to send:</strong></p>
  
  <pre><code>&lt;button type='button' data-a='".$fila['idPlaza']."' href='#editarUsuario' class='modalEditarUsuario btn btn-warning btn-xs' data-toggle='modal' data-backdrop='static' data-keyboard='false' title='Editar usuario'&gt;&lt;img src='../images/edit.png' width='20px' height='20px'&gt;&lt;/button&gt;
  </code></pre>
  
  <p><strong>Then I have this js code to send the value:</strong></p>
  
  <pre><code>    $(document).on("click", ".modalEditarUsuario", function (e) {
          e.preventDefault();
  
          var self = $(this);
  
          $("#a").val(self.data('a'));
  
          $(self.attr('href')).modal('show');
      });
  </code></pre>
  
  <p>Finally I have this bootstrap modal</p>
  
  <pre><code>&lt;!-- MODAL EDITAR--&gt;
  &lt;div id="editarUsuario" class="modal fade modal" role="dialog"&gt;
  &lt;div class="vertical-alignment-helper"&gt;
      &lt;div class="modal-dialog vertical-align-center"&gt;
          &lt;div class="modal-content"&gt;
              &lt;div class="modal-header"&gt;
                  &lt;button type="button" class="close" data-dismiss="modal"&gt;&amp;times;&lt;/button&gt;
                  &lt;h2 class="modal-title"&gt;Editar usuario&lt;/h2&gt;
              &lt;/div&gt;
              &lt;form name="formularioModificaUsuario" method='post' action="usuarios.php"&gt;
              &lt;div class="modal-body"&gt;
                  &lt;input type="text" class="form-control" name="idPlaza" id="a"&gt;
                  &lt;?php 
                      $valueA = ???
                  ?&gt;
              &lt;/div&gt;
              &lt;div class="modal-footer"&gt;
                  &lt;button type="reset" id="cancelar" class="btn btn-danger" data-dismiss="modal" value="reset"&gt;&lt;img src='../images/cancel.png' width='20px' height='20px'&gt; Cancelar&lt;/button&gt;
                  &lt;button type="submit" name="submitModifica" id="submit" class="btn btn-primary" value="submit"&gt;&lt;img src='../images/save_changes.png' width='20px' height='20px'&gt; Guardar cambios&lt;/button&gt;
              &lt;/div&gt;
              &lt;/form&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>My question is, how could I get the value of <code>id='a'</code> input into php variable <code>$valueA</code> to use after?</p>