Hola,
Your error 'Server request' occurs because your PHP script proveedorctrl.php is not encoded in UTF-8.
It's the same for your PHP script created for the view Proveedores: that's for this reason the accentuated characters are not properly displayed.
I suppose your PHP scripts are currently encoded in ANSI.
To convert your scripts in UTF-8, you can use for example Notepad++ and select in the menu Encoding, the menu item 'Convert to UTF-8 without BOM'.
Let me know, once your scripts will be converted, if your problem is finally solved.
Regards,
Pascal MARTINEZ