Frameset for php

I created a table instead of using frames.
What I want to achieve is to have the menu links load in the table center row
as if I was using frames, I want all the page links to load in the homepage table center row;
I was trying this:


link1="page1.php";
link2="page2.php";
link3="page3.php";
if (link1) {
include_once("page1.php");}
else if (link2) {
include_once("page2.php");}
else {
include_once("page3.php");}

My logics for the was if link1 is clicked page1.php would be displayed in the center table row, else if link2 is clicked page2.php would be displayed in the center table row, else
link3 is clicked page3.php would be displayed in the center table row;

I need the correct coding as this is not working.

A valid PHP variable must beging with ‘$’ . I don’t see anything else that’s obviously wrong, though I have one suggestion. Instead of include_once, use require_once. This will stop execution of the script if it is unable to include one of your PHP files, which is almost always the desirable response.

Ok, yes ‘$’ for variable declaration, I was on vacation, so I have not written any program in a while.
Respect. I’ll try to solve the issue, if not I’ll seek help.
Thanks

I want the links to be displayed in the center when the users click it.


//check to see which link is clicked and displays it in the table center row 
if ($link1) {
page1Function();
}
else if ($link2) {
page2Function();
}
else {
page3Function();
}

This is how this section of it should looks, below:

How can I establish this.?
If a use clicks 'link1’in the first column, its content displays in the second column.
and the same process for the other links.