Miscellany

<?php
$page = "<html><br>foo</br>\n<a href='foo'>bar<a>\n<br>baz</br>\n<br>baz</br>\n<br>baz</br></html>";

$page = explode ("\n", $page);



for ($i = 0; $i < count($page); $i++) {
        if (0 != preg_match('/<br>/i', $page[$i] )) {
                $r++;
        }
}

$r2 = rand(0, $r);
for ($i = 0; $i < count($page); $i++) {
        if (0 != preg_match('/<br>/i', $page[$i] ) and $i == $r2) {
                
                $page[$i] = preg_replace('<br>', 'yourtext' , $page[$i]);
                $r++;
        }
}


var_dump($page);
?>