core-bundle/src/Resources/contao/library/Contao/Widget.php
public function validate()
	{
		$varValue = $this->validator($this->getPost($this->strName));

		if ($this->hasErrors())
		{
			$this->class = 'error';
		}

		$this->varValue = $varValue;
	}
public function validate()
	{
		$varValue = $this->validator($this->getPost($this->strName));

		if ($this->hasErrors())
		{
			$this->class = 'error';
		}

		$this->varValue = $varValue;
	}
Validate the user input and set the value