src/Core/Db/Expression/Condition.php
public function isNull(ColumnInterface $column)
	{
		$columnName = ($column->getAlias()) ?: $column->getColumnName();
		$condition  = $columnName . ' IS NULL';
		$this->_addCondition($condition);

		return $this;
	}
public function isNull(ColumnInterface $column)
	{
		$columnName = ($column->getAlias()) ?: $column->getColumnName();
		$condition  = $columnName . ' IS NULL';
		$this->_addCondition($condition);

		return $this;
	}
public function isNull ( ColumnInterface $ column ) { $ columnName = ( $ column -> getAlias ( ) ) ? : $ column -> getColumnName ( ) ; $ condition = $ columnName . ' IS NULL' ; $ this -> _addCondition ( $ condition ) ; return $ this ; }
Add an is null condition to the condition array.
The order of the method call is important, in which way the condition string will
concatenate.

@param ColumnInterface $column Name of the column to compare.

@return $this The same instance to concatenate methods.
Add an is null condition to the condition array . The order of the method call is important in which way the condition string will concatenate .