- strstr: documentation ( source)
- strrev: documentation ( source)
- str_split: documentation ( source)
<?php
function longest_palendrome($string)
{
$current = $longest = '';
foreach (str_split(strrev($string)) as $char) {
if (strstr($string, $current . $char)) {
$current .= $char;
} elseif (!empty($current) && strlen($current) > strlen($longest)) {
$longest = $current;
$current = '';
}
}
return $longest;
}
echo longest_palendrome("i ama racecar ama aaaaaaaabbbbbbbbaaaaaaaa");