正则表达式以_开头的文件夹

hi I'm writing a script to loop through the current directory and list all sub directories all is working fine but i can't get it to exclude folders starting with an _

<?php

$dir = __dir__;

// Open a known directory, and proceed to read its contents
if (is_dir($dir)) {
    if ($dh = opendir($dir)) {
        echo("<ul>");
    while (($file = readdir($dh)) !== false) {
        if ($file == '.' || $file == '..' || $file == '^[_]*$' ) continue;
        if (is_dir($file)) {
            echo "<li> <a href='$file'>$file</a></li>";
        }
    }
    closedir($dh);
}
}
?>

you can use substr^[docs] like :

||  substr($file, 0, 1) === '_'

No need for a regex, use $file[0] == '_' or substr($file, 0, 1) == '_'

If you do want a regex, you need to use preg_match() to check: preg_match('/^_/', $file)

Or, if you would like to use regexp, you should use regex functions, like preg_match: preg_match('/^_/', $file); but as said by ThiefMaster, in this case a $file[0] == '_' suffices.

A more elegant solution is to use SPL. The GlobIterator can help you out. Each item is an instance of SplFileInfo.

<?php

$dir = __DIR__ . '/[^_]*';
$iterator = new GlobIterator($dir, FilesystemIterator::SKIP_DOTS);

if (0 < $iterator->count()) {
    echo "<ul>
";
    foreach ($iterator as $item) {
        if ($item->isDir()) {
            echo sprintf("<li>%s</li>
", $item);
        }
    }
    echo "</ul>
";
}