Task 25

<?php
$s = ('Pig latin is cool');
$arr = explode(" ", $s);
$prefix = $arr;
$postfix = $arr;
$result = [];
array_walk($prefix, function(&$x) {$x = ($x[0].'ay'); } );
array_walk($postfix, function(&$x) {$x=substr($x, 1); } );
    foreach($postfix as $key=>$value) {
        $result[] = $value.$prefix [$key];
    }
var_dump($result);

from Artur
<?php
$s = ('Pig latin is cool');
$arr = explode(" ", $s);

foreach ($arr as &$item) {
    $item = substr($item, 1) . $item[0] . 'ay';
}

var_dump($arr);