Hello,

On which event do you want to show alert?
If you tell exact scenario, it will help.

In an insert () before recording a record. check that there is no such record. If so, the dialog box should say "Document already entered."

Use
phpgrid_error("Document already entered.");
or
phpgrid_msg("Document already entered.");

Dear, the phpgrid_error instruction ("message") works, but pressing F12 in Chrome see that generates a "500 (Internal Server Error)". And phpgrid_msg ("message") instruction, shows no sign.

Please refer demos/editing/bulk-edit.php (line 150)
Try setting description using custom button. It will show the alert box.