original_string: public function remove_prefix($field) {
          if (preg_match('~^(-?_?)' . preg_quote($this->extraprefix, '~') . '(.*)$~', $field, $matches)) {
              return $matches[1] . $matches[2];
          } else {
              return null;
          }
      }
code: public function remove_prefix($field) {
          if (preg_match('~^(-?_?)' . preg_quote($this->extraprefix, '~') . '(.*)$~', $field, $matches)) {
              return $matches[1] . $matches[2];
          } else {
              return null;
          }
      }
code_tokens: public function remove_prefix ( $ field ) { if ( preg_match ( '~^(-?_?)' . preg_quote ( $ this -> extraprefix , '~' ) . '(.*)$~' , $ field , $ matches ) ) { return $ matches [ 1 ] . $ matches [ 2 ] ; } else { return null ; } }
docstring: Remove the extra prefix from a field name if it is present.
  @param string $field the extended field name.
  @return string the field name with the extra bit of prefix removed, or
  null if the extre prefix was not present.
docstring_tokens: Remove the extra prefix from a field name if it is present .