字符串清理，以支持ñ，á，é，í，ó，ú等特殊字符

I'm currently using this script to sanitize a block of text...

function rseo_sanitize($s) {
    $result = preg_replace("/[^a-zA-Z0-9'-]+/", "", html_entity_decode($s, ENT_QUOTES));
    return $result;
}

I'd like to add support for a collection of special characters such as ñ, á, é, í, ó, ú, etc

How can I integrate those (and the larger collection of spanish characters) into the preg_replace?

You can use /\pL+/u to match all letter symbols in Unicode.

There is no separate plane for Spanish letters only in PCRE, but you could try:

 /[^\p{Latin}0-9'-]+/u

This includes everything from the ISO Latin-1 charset I believe. That encompasses other european languages, not just spanish. But otherwise you would really have to list the desired letters individually.

You should use the \w along with the u modifier

Example:

/[^\w]+/u