Select record by date

I have the following function:

    public function findDate($empcode, $seldate, $hora) {
        // query to select all user records
        $query = "SELECT * FROM " . $this->table_name . "
                                    WHERE cdempid = ? AND cddate = ? AND cdtime = ?";

        // prepare query statement
        $stmt = $this->conn->prepare($query);

        // bind limit clause variables

        /*$srch_date = "$fecha";
        $srch_time = "$hora"; */

        $stmt->bindParam(1, $empcode, PDO::PARAM_INT);
        $stmt->bindParam(2, $seldate);
        $stmt->bindParam(3, $hora);

        // execute query
        $stmt->execute();

        // return row count
        return $stmt;

And it is called from another program. This is the line that calls it:

        $stmt = $citas->findDate($empcode, $seldate, $hora);
        //$stmt = $citas->findDate($empcode, "20180329", $hora);

When I call it using the $ seldate variable, it does not find any records, but when I use the line that appears documented if it finds them. Now save the value that $ seldate brings and it is a correct date, which comes from a function in angular.

This is where you assign the value:

$data = json_decode(file_get_contents("php://input"));

$empcode = $data->empcode;
$seldate = $data->cddiacita;

This is the Angular function that calls the loadtime.php program, passing the date parameter that it takes from an angle type date input.

    var app = angular.module ("myapp", []);     app.controller ("usercontroller", function ($ scope, $ http) {

    $scope.loadEmployee = function(){
        $http.get("loadEmp.php")
        .success(function(data){
                $scope.empleados = data;
        });
    };

    $scope.loadService = function(){
        $http.post("loadSrv.php", {'empcode':$scope.empleado})
        .success(function(data){
                $scope.servicios = data;
        });

        $http.post("loadTime.php", {'empcode':$scope.empleado, 'cddiacita':$scope.fecha.value})
        .success(function(data){
                $scope.horarios = data;
        });
    };

    $scope.fecha = {
        value: new Date(),
        currentDate: new Date()
    };        
});

I already tried the bindParam usandp PDO :: PARAM_STR. Also use convert. I do not know why he is not taking it as a valid date. Any suggestions?