Redirect error in PHP

Today I upload to my host a simple program developed in PHP mini3, the error is in the redirect the constant URL

<?php echo URL?>login/validarL

this link carries to controller and finally carries the function´s controller
so I wanna repair this error because nothing can run successfully

What is your domain/website name??

https://mdosoft.000webhostapp.com/
this,if you click the button automatically he takes you to error page

Let me check and get back to you.

Make sure you have uploaded all your files.

Yes am sure, i have a copy and this copy works full, i don´t what´s the error, in theory this action validate the system access

Is it supposed to be like this?