onSubmit(form:NgForm) {

   this.subscription = this._validation.validation({
        cell_no: form.value.cell_no, pass: form.value.password,
        username: this._common.getConnData().username, password:this._common.getConnData().password
    })
    .subscribe(res => {
         if(typeof res == 'string') // invalid access attempt
         {
               this.invalid_access = true;
         }
         else // login successful
         {
            console.log(res);
         }
    })

validation(data:{})
{
    const body = JSON.stringify(data);
    const headers = new Headers();
    headers.append('Content-Type', 'application/json');

    return this._http.post(this._common.getBaseUrl()+"doctor_panel_api/validation_modified/format/json",
    body, {headers: headers})
    .map(res => res.json());
 }