随机链接php

I am trying to setup this code that loads a random link but I have one problem:

$links = file('myfile.txt');
$rand_link = $links[ mt_rand(0, count($links) - 1) ];
echo '<div class="link"><a href="' . $rand_link . '"><img src="button.png" border="0"></a></div>';

It sometimes shows the pages it has shown earlier. I want it to remember what sites it has displayed and don’t show it again until the user starts from the beginning. Thanks appreciate your help.

finally the enhanced version with multiple sites in history

// Predefinitions
$links = file('myfile.txt');
$currentPage = $_SERVER['PHP_SELF'];

// make sure links are pure and no whitespaces are left
foreach ( $links as &$link )
{
    $link = trim($link);
}

// prepare for history
if ( ! array_key_exists('visited_links', $_SESSION) )
{
    $_SESSION['visited_links'] = array();
}
// add current site to visited links if it wasnt visited earlier
if ( ! in_array($currentPage, $_SESSION['visited_links']) )
{
    $_SESSION['visited_links'][] = $currentPage; 
}

// get all those links which weren't visited yet kinda $links = $allLinks - $visitedLinks
$potentialLinks = array_diff($links, $_SESSION['visited_links']);

$randomLinkId = mt_rand(0, count($potentialLinks)-1);
$randomLinkIds = array_keys($potentialLinks);
$randomLink = $potentialLinks[$randomLinkIds[$randomLinkId]];


echo '<div class="link"><a href="'.$randomLink.'"><img src="button.png" border="0"></a></div>';

there could be potential errors if the format of $_SERVER['PHP_SELF'] and this of your linklist differ, you can evaluate this with some quick var_dumps. As far as I know Wordpress automatically starts an session, this should explain your errormessage. This script assumes that the session is already started.

Try this code. May be errors, I have not tested on the server. And I use the session to preserve already viewed pages.

$links = file('myfile.txt');
$show_links = array();

session_start();

if( $_SESSION['show_links'] )
foreach($_SESSION['show_links'] as $key=>$value){
    $show_links[$key] = $value;
}

$random_link_number = mt_rand(0, count($links) - 1);

if(count($show_links) != count($links)){
while(   !in_array($random_link_number, $show_links)   ){
   $random_link_number = mt_rand(0, count($links) - 1);
}
}
else{
    unset($show_links);
}

$show_links[] = $random_link_number;
$_SESSION['show_links'] = $show_links;

$rand_link = $links[ $random_link_number ];