you can have multiple links in a file, but if you include it, all the links will be included.
for example.
links1.php:
<a href = mylink1.com>mylink1</a>
<a href = mylink2.com>mylink2</a>
<a href = mylink3.com>mylink3</a>
links2.php
<a href = mylink4.com>mylink4</a>
<a href = mylink5.com>mylink5</a>
<a href = mylink6.com>mylink6</a>
then in your main php file:
include ('links1.php');
blah blah blah
blah blah blah
include ('links2.php');
would net you something like this on the output in your main php file:
mylink1
mylink2
mylink3
blah blah blah
blah blah blah
mylink4
mylink5
mylink6
Is that what you were looking for? Or do you want to store all of your links in one file, then just reference them one by one from that textfile into your main file? If so, I can show you how to do that as well...