public static function encode_dbname($st, $maxlength = 50): string
  {
    $st = self::remove_accents(self::cast($st));
    $res = '';

    if ( !\is_int($maxlength) ){
      $maxlength = mb_strlen($st);
    }

    for ( $i = 0; $i < $maxlength; $i++ ){
      if ( mb_ereg_match('[A-z0-9]',mb_substr($st,$i,1)) ){
        $res .= mb_substr($st,$i,1);
      }
      else if ( (mb_strlen($res) > 0) &&
        (mb_substr($res,-1) != '_') &&
        ($i < ( mb_strlen($st) - 1 )) ){
        $res .= '_';
      }
    }
    if ( substr($res, -1) === '_' ){
      $res = substr($res, 0, -1);
    }
    return $res;
  }
public static function encode_dbname($st, $maxlength = 50): string
  {
    $st = self::remove_accents(self::cast($st));
    $res = '';

    if ( !\is_int($maxlength) ){
      $maxlength = mb_strlen($st);
    }

    for ( $i = 0; $i < $maxlength; $i++ ){
      if ( mb_ereg_match('[A-z0-9]',mb_substr($st,$i,1)) ){
        $res .= mb_substr($st,$i,1);
      }
      else if ( (mb_strlen($res) > 0) &&
        (mb_substr($res,-1) != '_') &&
        ($i < ( mb_strlen($st) - 1 )) ){
        $res .= '_';
      }
    }
    if ( substr($res, -1) === '_' ){
      $res = substr($res, 0, -1);
    }
    return $res;
  }
public static function encode_dbname ( $ st , $ maxlength = 50 ) : string { $ st = self :: remove_accents ( self :: cast ( $ st ) ) ; $ res = '' ; if ( ! \ is_int ( $ maxlength ) ) { $ maxlength = mb_strlen ( $ st ) ; } for ( $ i = 0 ; $ i < $ maxlength ; $ i ++ ) { if ( mb_ereg_match ( '[A-z0-9]' , mb_substr ( $ st , $ i , 1 ) ) ) { $ res .= mb_substr ( $ st , $ i , 1 ) ; } else if ( ( mb_strlen ( $ res ) > 0 ) && ( mb_substr ( $ res , - 1 ) != '_' ) && ( $ i < ( mb_strlen ( $ st ) - 1 ) ) ) { $ res .= '_' ; } } if ( substr ( $ res , - 1 ) === '_' ) { $ res = substr ( $ res , 0 , - 1 ) ; } return $ res ; }
Returns a corrected string for database naming.

```php
\bbn\x::dump(\bbn\str::encode_dbname('my.database_name ? test  :,; !plus'));
// (string) "my_database_name_test_plus"
```

@param string $st The name as string.
@param int $maxlength The maximum length, default: "50".
@return string
Returns a corrected string for database naming .