php - My Input type button in div class is not submitting

You need to declare your button as 'submit', instead of 'button'.

Instead of

declare it this way

A submit type input does exactly what comes to your mind when you read it - it submits the form. You can have multiple buttons within your form, but it is a good practice to keep only one submit button whose job is to send the form information wherever needed.

Please read some of the following HTML guides to get a better understanding on how things need to be done:

https://www.w3schools.com/html/html_forms.asp

https://www.w3schools.com/html/html_form_input_types.asp