Passing data via Modal Bootstrap and getting php variable?

<button type='button' data-a="<?echo $fila['idPlaza'];?>" href='#editarUsuario' class='modalEditarUsuario btn btn-warning btn-xs' data-toggle='modal' data-backdrop='static' data-keyboard='false' title='Editar usuario'>
    <img src='../images/edit.png' width='20px' height='20px'>
</button>

Put below code in footer before end of </body> tag.

<!-- MODAL EDITAR-->
<div id="editarUsuario" class="modal fade modal" role="dialog">
    <div class="vertical-alignment-helper">
        <div class="modal-dialog vertical-align-center">
        <div class="modal-content">


        </div>
        </div>
    </div>
</div>

Use Script like this.

<script>
    $('.modalEditarUsuario').click(function(){
        var ID=$(this).attr('data-a');
        $.ajax({url:"NewPage.php?ID="+ID,cache:false,success:function(result){
            $(".modal-content").html(result);
        }});
    });
</script>

Create NewPage.php, and paste the below code. (Remember, this page name NewPage.php is used in script tag also. if you are planning to change the name of this page, change page name there in script tag too. Both are related.)

<?
$ID=$_GET['ID'];
?>
<div class="modal-header">
   <button type="button" class="close" data-dismiss="modal">&times;</button>
   <h2 class="modal-title">Editar usuario</h2>
</div>
<form name="formularioModificaUsuario" method='post' action="usuarios.php">
    <div class="modal-body">
        <input type="text" class="form-control" name="idPlaza" id="a">
        <?php 
            $valueA = $ID;
        ?>
    </div>
    <div class="modal-footer">
        <button type="reset" id="cancelar" class="btn btn-danger" data-dismiss="modal" value="reset">
        <img src='../images/cancel.png' width='20px' height='20px'> Cancelar</button>
        <button type="submit" name="submitModifica" id="submit" class="btn btn-primary" value="submit">
        <img src='../images/save_changes.png' width='20px' height='20px'> Guardar cambios</button>
    </div>
</form>

A more updated answer is found below: https://.com/a/44391959/1004312

You are opening a modal from another modal and closing the first. If you're using Bootstrap 3, you can do the following:

DEMO: http://jsbin.com/venek/1/edit

In the first modal put the link to the next modal (#modal-1 & #modal-2 are example ids)

  <a href="#modal-2" data-toggle="modal" data-dismiss="modal">Next</a>

In the second modal put the link to the first:

  <a href="#modal-1" data-toggle="modal" data-dismiss="modal">Previous</a>

DEMO: http://jsbin.com/venek/1/edit

Send the key via resolve as a parameter (see plunker):

angular.module('plunker', ['ui.bootstrap']);
var ModalDemoCtrl = function ($scope, $modal, $log) {

  var key = 1000;
  $scope.items = ['item1', 'item2', 'item3'];

  $scope.open = function () {

    var modalInstance = $modal.open({
      templateUrl: 'myModalContent.html',
      controller: ModalInstanceCtrl,
      resolve: {
        items: function () {
          return $scope.items;
        },
        key: function() {return key; }
      }
    });

    modalInstance.result.then(function (selectedItem) {
      $scope.selected = selectedItem;
    }, function () {
      $log.info('Modal dismissed at: ' + new Date());
    });
  };
};

// Please note that $modalInstance represents a modal window (instance) dependency.
// It is not the same as the $modal service used above.

var ModalInstanceCtrl = function ($scope, $modalInstance, items, key) {

  alert("The key is " + key)
  $scope.items = items;
  $scope.selected = {
    item: $scope.items[0]
  };

  $scope.ok = function () {
    $modalInstance.close($scope.selected.item);
  };

  $scope.cancel = function () {
    $modalInstance.dismiss('cancel');
  };
};