Library of Babel Page Generation

<?php
$search_text = "          this is some random text          ";
$length = strlen($search_text);

$alphabet = "abcdefghijklmnopqrstuvwxyz ,.";

$before = random_int(0, (3200 - $length));
$after = 3200 - $before - $length;

$page = "";

for($i=0; $i<$before; $i++)
{
    $page .= $alphabet[random_int(0, 28)];
}

$page .= $search_text;

for($i=0; $i<$after; $i++)
{
    $page .= $alphabet[random_int(0, 28)];
}

echo "<pre>" . chunk_split($page, 80, "<br>") . "</pre>";