全くの初心者でこれを作るのに3ヶ月かかった恥ずかしいけど晒すぜ
<?php
header('Content-Type: text/html; charset=UTF-8');
date_default_timezone_set('Asia/Tokyo');
$log = 'log.txt';
$name = 'nanashi';
if (@$_POST['name'] && @$_POST['comment']) {
$name = $_POST['name'];
$now = date('y/m/d H:i');
file_put_contents($log, mb_convert_encoding("{$_POST['name']}<>{$_POST['comment']}<>{$now}\n", 'UTF-8', 'UTF-8'),

FILE_APPEND | LOCK_EX);
}
$read = file($log);
array_map(function($a){
return mb_convert_encoding($a, 'UTF-8', 'auto');
}, $read);
$len = count($read) - 1;
?>
<form method="post">
Name;<input type="text" name="name" size="10" maxlength="10" value="<?php echo $name; ?>">
Comment:<input type="text" name="comment" size="50" maxlength="50">
<input type="submit">
</form>
<ul>
<?php
for ($i = $len; $i >= 0; $i--) {
$src = explode('<>', $read[$i]);
echo '<li>' . htmlspecialchars("{$src[0]}:{$src[1]}({$src[2]})", ENT_QUOTES, 'UTF-8') . '</li>';
}
?>
</ul>