ループは1回にできると思うけどまぁとりあえず。
<?php
$str = <<<EOD
<html>
<body>
<center>
<form action="confirm.php" method="get">
<input type="text" name="name"><br>
<input type="submit" value="submit">
</center>
</form>
</body>
</html>
EOD;
preg_match_all("/<.*?>/", $str, $matches);
//var_dump($matches);
$ary = array();
$stack = array();
foreach ($matches[0] as $key => $value) {
array_push($ary, $value);
}
foreach ($ary as $key => $value) {
if (preg_match("/<\/([a-zA-Z]+)/", $value, $tag)) {
# echo "$value\n";
# var_dump($tag[1]);
$isFoundClose = false;
foreach ($ary as $k => $v) {
if (preg_match("/<{$tag[1]}/", $v)) {
# echo "match\n";
$isFoundClose = true;
array_splice($ary, $k, $key - $k);
break;
}
}
if (!$isFoundClose) {
echo "error:$value\n";
}
}
else {
}
}