Returns true if string contains only alphabetic characters. Numbers, punctuation, whitespace, and another other special characters will cause a false.
secret_phrase: abcdefgeven_more_secret_phrase: abc123{{ if secret_phrase | is_alpha }}{{ if even_more_secret_phrase | is_alpha }}@if (Statamic::modify($secret_phrase)->isAlpha()->fetch()) @endif@if (Statamic::modify($even_more_secret_phrase)->isAlpha()->fetch()) @endiftruefalse
