[PHP] Bug with headers

Description

You should not overwrite the headers

Here is the JSON: https://github.com/dansleboby/ubity-sdk-php/blob/master/swagger.json#L307

Suggest a fix/enhancement

The elseif for application/json overwrite the wanted headers in my YAML

I use

'application/json;version=1'

FIX:
Remove elseif and content

In: https://github.com/swagger-api/swagger-codegen/blob/47f355a24100dbf8f7cfa242a0ab8462774ac0a1/samples/client/petstore/php/SwaggerClient-php/lib/HeaderSelector.php

 /**
     * Return the header 'Accept' based on an array of Accept provided
     *
     * @param string[] $accept Array of header
     *
     * @return string Accept (e.g. application/json)
     */
    private function selectAcceptHeader($accept)
    {
        if (count($accept) === 0 || (count($accept) === 1 && $accept[0] === '')) {
            return null;
        } elseif (preg_grep("/application\/json/i", $accept)) {
            return 'application/json';
        } else {
            return implode(',', $accept);
        }
    }

    /**
     * Return the content type based on an array of content-type provided
     *
     * @param string[] $contentType Array fo content-type
     *
     * @return string Content-Type (e.g. application/json)
     */
    private function selectContentTypeHeader($contentType)
    {
        if (count($contentType) === 0 || (count($contentType) === 1 && $contentType[0] === '')) {
            return 'application/json';
        } elseif (preg_grep("/application\/json/i", $contentType)) {
            return 'application/json';
        } else {
            return implode(',', $contentType);
        }
    }

Start with the PHP HeaderSelector.php referenced in the issue and compare selectAcceptHeader and selectContentTypeHeader with the supplied Swagger JSON at line 307. Verify how an Accept value such as application/json;version=1 is handled, then confirm that the generated client preserves the requested header rather than replacing it with application/json.