Question: i need to switch between two variables so i am able to serve two variables equally

for example i have 

```
$ad1
$ad2

```

i want to serve both ads equally using a light method with no database

using random method won't serve both equally

can you please guide me how to achieve this ?

Answer: 
But the random method (50/50) should serve both equally, given enough requests.

And it is the simplest solution imho.

```
<?php
$ad1 = '<img src... >';
$ad2 = '<img src...2 >';

echo mt_rand(0, 1) ? $ad1 : $ad2;
?>

```
* You can use memcache (recommended)
* You can keep track of the last used variable in a file on the server (not recommended)
* You can use time() and use its mod by 2 as your decision maker (still not an exactly equality as you wanted)

(I think, on the long run, rand will serve you great)