src/Valkyrja/HttpMessage/MessageTrait.php
public function withoutHeader(string $name)
    {
        if (! $this->hasHeader($name)) {
            return clone $this;
        }

        $normalized = strtolower($name);
        $original   = $this->headerNames[$normalized];
        $new        = clone $this;

        unset($new->headers[$original], $new->headerNames[$normalized]);

        return $new;
    }
public function withoutHeader(string $name)
    {
        if (! $this->hasHeader($name)) {
            return clone $this;
        }

        $normalized = strtolower($name);
        $original   = $this->headerNames[$normalized];
        $new        = clone $this;

        unset($new->headers[$original], $new->headerNames[$normalized]);

        return $new;
    }
Return an instance without the specified header.

Header resolution MUST be done without case-sensitivity.

This method MUST be implemented in such a way as to retain the
immutability of the message, and MUST return an instance that removes
the named header.

@param string $name Case-insensitive header field name to remove.

@return static