core-bundle/src/Resources/contao/library/Contao/Model/Collection.php
public function fetchEach($strKey)
	{
		$this->reset();
		$return = array();

		while ($this->next())
		{
			$strPk = $this->current()->getPk();

			if ($strKey != 'id' && isset($this->$strPk))
			{
				$return[$this->$strPk] = $this->$strKey;
			}
			else
			{
				$return[] = $this->$strKey;
			}
		}

		return $return;
	}
public function fetchEach($strKey)
	{
		$this->reset();
		$return = array();

		while ($this->next())
		{
			$strPk = $this->current()->getPk();

			if ($strKey != 'id' && isset($this->$strPk))
			{
				$return[$this->$strPk] = $this->$strKey;
			}
			else
			{
				$return[] = $this->$strKey;
			}
		}

		return $return;
	}
Fetch a column of each row

@param string $strKey The property name

@return array An array with all property values