<?php
function persuade_name($name)
{
$persuade = ['ая' => 'е', 'бвгджзклмнпрстфхцчшщ' => '+у', 'й' => 'ю'];
foreach ($persuade as $search => $replacement) {
if ($last = mb_substr($name, -1) and mb_stripos($search, $last) !== false) {
if (mb_strtoupper($last) === $last) {
$replacement = mb_strtoupper($replacement);
}
if (substr($replacement, 0, 1) == '+') {
$name .= substr_replace($replacement, '', 0, 1);
} else {
$name = preg_replace('/.$/u', $replacement, $name);
}
break;
}
}
return $name;
}
echo persuade_name('Сергей'); // Сергею