/home/joan/000www/repo/spirit/1.0/core/extensions/filter/base_filters/alpha_filter.php

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<?php
class AlphaFilter implements FilterInterface
{
    public static function execute ($s, $options)
    {
        $patron = '/[^a-zA-Z\s]/';
        return preg_replace($patron, '', (string) $s);
    }
}

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