Code:

 

<?php
// Create the array
$sig = array();

// Add values into the array
$sig[0] = "First sig";
$sig[1] = "Second sig";
$sig[2] = "Third sig";

// Randomize a number between 0 and the size of the array
$number = rand(0,sizeof($sig));

// Output the array element with the number of the randomizer
echo $sig[$number];
?>