src/net/http/HttpRequest.php
public function getHeader($name) {
        if (!is_string($name)) throw new IllegalTypeException('Illegal type of parameter $name: '.gettype($name));
        if (!strlen($name))    throw new InvalidArgumentException('Invalid argument $name: '.$name);

        $headers = $this->getHeaders($name);
        if ($headers)
            return join(', ', $headers);    // combine multiple headers of the same name according to RFC
        return null;
    }
public function getHeader($name) {
        if (!is_string($name)) throw new IllegalTypeException('Illegal type of parameter $name: '.gettype($name));
        if (!strlen($name))    throw new InvalidArgumentException('Invalid argument $name: '.$name);

        $headers = $this->getHeaders($name);
        if ($headers)
            return join(', ', $headers);    // combine multiple headers of the same name according to RFC
        return null;
    }
public function getHeader ( $ name ) { if ( ! is_string ( $ name ) ) throw new IllegalTypeException ( 'Illegal type of parameter $name: ' . gettype ( $ name ) ) ; if ( ! strlen ( $ name ) ) throw new InvalidArgumentException ( 'Invalid argument $name: ' . $ name ) ; $ headers = $ this -> getHeaders ( $ name ) ; if ( $ headers ) return join ( ', ' , $ headers ) ; // combine multiple headers of the same name according to RFC return null ; }
Return the request header with the specified name. This method returns the value of a single header.

@param  string $name - header name (case is ignored)

@return string|null - header value or NULL if no such header was found
Return the request header with the specified name . This method returns the value of a single header .