src/QueryModifierBuilder.php
public function groupBy( array $expressions )  {
		foreach ( $expressions as $expression ) {
			$this->expressionValidator->validate( $expression,
				ExpressionValidator::VALIDATE_VARIABLE | ExpressionValidator::VALIDATE_FUNCTION_AS
			);
		}

		$expression = implode( ' ', $expressions );
		$this->usageValidator->trackUsedPrefixes( $expression );
		$this->usageValidator->trackUsedVariables( $expression );
		$this->modifiers['GROUP BY'] = $expression;
	}
public function groupBy( array $expressions )  {
		foreach ( $expressions as $expression ) {
			$this->expressionValidator->validate( $expression,
				ExpressionValidator::VALIDATE_VARIABLE | ExpressionValidator::VALIDATE_FUNCTION_AS
			);
		}

		$expression = implode( ' ', $expressions );
		$this->usageValidator->trackUsedPrefixes( $expression );
		$this->usageValidator->trackUsedVariables( $expression );
		$this->modifiers['GROUP BY'] = $expression;
	}
public function groupBy ( array $ expressions ) { foreach ( $ expressions as $ expression ) { $ this -> expressionValidator -> validate ( $ expression , ExpressionValidator :: VALIDATE_VARIABLE | ExpressionValidator :: VALIDATE_FUNCTION_AS ) ; } $ expression = implode ( ' ' , $ expressions ) ; $ this -> usageValidator -> trackUsedPrefixes ( $ expression ) ; $ this -> usageValidator -> trackUsedVariables ( $ expression ) ; $ this -> modifiers [ 'GROUP BY' ] = $ expression ; }
Sets the GROUP BY modifiers.

@param string[] $expressions
Sets the GROUP BY modifiers .