Smopp_v2/api/models/HelperModel.php

<?php

namespace app\models;

use Yii;
use yii\base\Model;

/**
 * ContactForm is the model behind the contact form.
 */
class HelperModel extends Model
{
    
    public static function stripWhitespaces($string) 
    {
        $old_string = $string;
        $string = strip_tags($string);
        $string = preg_replace('/([^\pL\pN\pP\pS\pZ])|([\xC2\xA0])/u', ' ', $string);
        $string = str_replace('  ',' ', $string);
        $string = trim($string);
        
        if ($string === $old_string) {
            return $string;
        } else {
            return self::stripWhitespaces($string); 
        }
    }
    
    public static function clearSectionString($string,$mask) 
    {
        $result = '';
        for ($i=0;$i < mb_strlen($string); $i++) {
            $lit = mb_substr($string, $i, 1, 'UTF-8');
            foreach ( $mask as $l) {
                //var_dump($lit .'==='. $l);
                if ( $lit === $l)  {
                        $result .= $lit;
                }
            }
        }
        $result = mb_strtoupper($result);
        return $result;
    }
}