Okay, for what you're talking about, it seems that you are using include a bit too much
Question 1
You can't make a button include a php file once the file is in your browser window. What you could do is make the button link to that php file, or link to the local file, with a variable in the request string, making PHP include the file itself.
[!--PHP-Head--][div class=\'phptop\']PHP[/div][div class=\'phpmain\'][!--PHP-EHead--][span style=\"color:#0000BB\"]<?
[/span][span style=\"color:#007700\"]if([/span][span style=\"color:#0000BB\"]$_GET[/span][span style=\"color:#007700\"][[/span][span style=\"color:#0000BB\"]includefile[/span][span style=\"color:#007700\"]]==[/span][span style=\"color:#0000BB\"]1[/span][span style=\"color:#007700\"]) {
include([/span][span style=\"color:#DD0000\"]\"myfile.php\"[/span][span style=\"color:#007700\"]);
}
[/span][span style=\"color:#0000BB\"]?>
[/span]<td align=\"left\" valign=\"top\" ><a href=\"thisfile.php?includefile=1\" target=\"_self\"><img src=\"aboutus.gif\" alt=\"Click here to view\" width=\"143\" height=\"35\" border=\"0\"></a></td>[/span][!--PHP-Foot--][/div][!--PHP-EFoot--]
Question 2
Once again use a variable on the URL, stay away from that include if you can
File 1
[!--PHP-Head--][div class=\'phptop\']PHP[/div][div class=\'phpmain\'][!--PHP-EHead--][span style=\"color:#0000BB\"]<?
[/span][span style=\"color:#FF8000\"]//successful database query here
[/span][span style=\"color:#0000BB\"]header[/span][span style=\"color:#007700\"]([/span][span style=\"color:#DD0000\"]\"Location: index.php?dbquerysuccess=1\"[/span][span style=\"color:#007700\"]);
[/span][span style=\"color:#0000BB\"]?>
[/span]
[/span][!--PHP-Foot--][/div][!--PHP-EFoot--]
File 2 (index.php)
[!--PHP-Head--][div class=\'phptop\']PHP[/div][div class=\'phpmain\'][!--PHP-EHead--][span style=\"color:#0000BB\"]<?
[/span][span style=\"color:#FF8000\"]//your code here
[/span][span style=\"color:#007700\"]if([/span][span style=\"color:#0000BB\"]$_GET[/span][span style=\"color:#007700\"][[/span][span style=\"color:#0000BB\"]dbquerysuccess[/span][span style=\"color:#007700\"]] == [/span][span style=\"color:#0000BB\"]1[/span][span style=\"color:#007700\"]) {
echo [/span][span style=\"color:#DD0000\"]\"Successful Database Query\"[/span][span style=\"color:#007700\"];
}
[/span][span style=\"color:#0000BB\"]?>[/span]
[/span][!--PHP-Foot--][/div][!--PHP-EFoot--]