src/Validator/Alpha.php
public function isValid($value)
    {
        $this->resetMessages();

        $this->value = $value;

        if (!is_string($value)) {
            $this->addMessage();

            return false;
        }

        if ($this->allowedChars !== '') {
            $value = str_replace(str_split($this->allowedChars), '', $value);
        }

        if (!ctype_alpha($value)) {
            $this->addMessage();

            return false;
        }

        return true;
    }
public function isValid($value)
    {
        $this->resetMessages();

        $this->value = $value;

        if (!is_string($value)) {
            $this->addMessage();

            return false;
        }

        if ($this->allowedChars !== '') {
            $value = str_replace(str_split($this->allowedChars), '', $value);
        }

        if (!ctype_alpha($value)) {
            $this->addMessage();

            return false;
        }

        return true;
    }
{@inheritdoc}