src/Csv.php
public function getIdField() {
	if(!empty($this->headers)
	&& !in_array($this->idField, $this->headers)) {
		throw new InvalidFieldException($this->idField);
	}

	return $this->idField;
}
public function getIdField() {
	if(!empty($this->headers)
	&& !in_array($this->idField, $this->headers)) {
		throw new InvalidFieldException($this->idField);
	}

	return $this->idField;
}
public function getIdField ( ) { if ( ! empty ( $ this -> headers ) && ! in_array ( $ this -> idField , $ this -> headers ) ) { throw new InvalidFieldException ( $ this -> idField ) ; } return $ this -> idField ; }
Retrieves the internally set field used for ID. By default, this is "ID",
but if there is no field with that name then this function returns null.

@return string|null Name of field, or null if the default field does not
exist in the CSV
Retrieves the internally set field used for ID . By default this is ID but if there is no field with that name then this function returns null .