How to know with php if a type button was clicked

I know by far that when you have

<input type="submit" name="reset-page-copy" value="reset to default" />  

it Works like this:

if(isset($_POST['reset-page-copy'])) { }

But lets suppose i have this:

<input type="button" name="reset-page-copy" value="reset to default" />  

Then what should i do?