Change a phrase and store in session ever X seconds

change.php

<?php
session_start();

$phrases = array(
  'Schizophasia, a mental condition characterized by incoherent babbling (compulsive or intentional, but nonsensical)',
  'Logorrhea, a mental condition characterized by excessive talking (incoherent and compulsive)',
  'Clanging, a speech pattern that follows rhyming and other sound associations rather than meaning',
  'Graphorrhea, a written version of word salad that is more rarely seen than logorrhea in people with schizophrenia.'
); 

$seconds = 10; 
if(time() % $seconds == 0 || !isset($_SESSION["phrase"])){
    $_SESSION["phrase"] = $phrases[rand(0, count($phrases)-1)];   
}

echo $_SESSION["phrase"];