Get the value of an HTTP header
The lookup is case insensitive.
@param string $headerName the HTTP header name, 'Content-Type' for example
@return boolean|string the value or false if not found
541597
public function getHeaderValue($headerName)
    {
        if (is_string($headerName) && count($this->headers) > 0) {
            $lowCaseHeaders = array_change_key_case($this->headers, CASE_LOWER);
            $lowCaseHeaderName = strtolower($headerName);
            if (isset($lowCaseHeaders[$lowCaseHeaderName])) {
                return $lowCaseHeaders[$lowCaseHeaderName];
            }
        }
        return false;
    }
305284
protected function header(string $name)
    {
        return isset($this->request->getHeaders()[$name]) ?
            $this->request->getHeaders()[$name][0] : null;
    }
905279
public function readHeader(string $headerName): ValueReader
    {
        return new ValueReader(
                $this->headers->errors(),
                $headerName,
                $this->headers->value($headerName)
        );
    }
587696
protected function seeHeader($headerName, $value = null)
    {
        $headers = $this->response->headers;

        $this->assertTrue($headers->has($headerName), "Header [{$headerName}] not present on response.");

        if (! is_null($value)) {
            $this->assertEquals(
                $headers->get($headerName), $value,
                "Header [{$headerName}] was found, but value [{$headers->get($headerName)}] does not match [{$value}]."
            );
        }

        return $this;
    }
1206724
public function get(string $name)
    {
        return isset($this->headers[$name]) ? $this->headers[$name] : null;
    }
1219015
function getHeaderValue($header){
		$header = strtolower($header);
		$headers = $this->getResponseHeaders(array("as_hash" => true, "lowerize_keys" => true));
		if(isset($headers["$header"])){ return $headers["$header"]; }
	}
795931
protected function getRateLimitValuesByHeader($headerName)
    {
        $header = $this->getHeaders()[$headerName];
        
        return $header ? array_reduce(explode(',', $header[0]), function ($limits, $limitStr) {
            list($count, $time) = explode(':', $limitStr, 2);
            $limits[$time] = (int) $count;
            
            return $limits;
        }, []) : null;
    }
85397
public String getHeaderValue(String name) {
        if (headers == null) {
            return null;
        }
        return headers.get(name);
    }
124875
public function getHeader($name)
    {
        assert(is_string($name));

        $name = strtolower($name);

        if (isset($this->_headers[$name])) {
            return $this->_headers[$name];
        }

        return null;
    }
563425
public function header($name, $default = null)
    {
        $header = $this->headers[strtolower($name)] ?? null;

        return $header ? $header->value() : $default;
    }
1037556
public function getHeader($name)
    {
        $headers = $this->message->getHeaders();
        return isset($headers[$name]) ? $headers[$name] : null;
    }
1274902
public function getHeader($name)
    {
        if (!$this->hasHeader($name)) {
            throw new \InvalidArgumentException(sprintf('The request header "%s" does not exist.', $name));
        }

        return $this->headers[$name];
    }
865785
public final function header(string $name, string $value = null)
    {
        return ($value === null) ? $this->getHeader($name) : $this->setHeader($name, $value);
    }
556446
public String getHeaderValue( String name )
    {
        for ( Header header : headers ) {
            if ( header.getName().equals( name ) ) {
                return header.getValue();
            }
        }
        return null;
    }
898252
public String value(String name) {
        final HttpHeader header = getHeader(name);
        return header == null ? null : header.value();
    }
362215
public function getHeaderValue($name)
    {
        $pattern = '#' . $name . ': (.*)#i';
        if (preg_match($pattern, $this->getResponseHeader(), $match)) {
            return $match[1];
        } else {
            return null;
        }
    }
976699
public function get($name)
    {
        if (is_null($name) || empty($name))
        {
            return null;
        }

        $loweredKey = strtolower($name);

        if (array_key_exists($loweredKey, $this->keyMap) === false)
        {
            return null;
        }

        $originalKey = $this->keyMap[$loweredKey];

        return $this->headerMap[$originalKey];
    }