public function setVerticalBorderChars(string $outside, string $inside = null): self
    {
        $this->verticalOutsideBorderChar = $outside;
        $this->verticalInsideBorderChar = $inside ?? $outside;

        return $this;
    }
public function setVerticalBorderChars(string $outside, string $inside = null): self
    {
        $this->verticalOutsideBorderChar = $outside;
        $this->verticalInsideBorderChar = $inside ?? $outside;

        return $this;
    }
public function setVerticalBorderChars ( string $ outside , string $ inside = null ) : self { $ this -> verticalOutsideBorderChar = $ outside ; $ this -> verticalInsideBorderChar = $ inside ?? $ outside ; return $ this ; }
Sets vertical border characters.

<code>
╔═══════════════╤══════════════════════════╤══════════════════╗
║ ISBN          │ Title                    │ Author           ║
╠═══════1═══════╪══════════════════════════╪══════════════════╣
║ 99921-58-10-7 │ Divine Comedy            │ Dante Alighieri  ║
║ 9971-5-0210-0 │ A Tale of Two Cities     │ Charles Dickens  ║
╟───────2───────┼──────────────────────────┼──────────────────╢
║ 960-425-059-0 │ The Lord of the Rings    │ J. R. R. Tolkien ║
║ 80-902734-1-6 │ And Then There Were None │ Agatha Christie  ║
╚═══════════════╧══════════════════════════╧══════════════════╝
</code>

@param string      $outside Outside border char (see #1 of example)
@param string|null $inside  Inside border char (see #2 of example), equals $outside if null
Sets vertical border characters .