Validating a URL in PHP

Check if the variable $url is a valid URL:

The FILTER_VALIDATE_URL filter validates a URL.

Possible  flags:

FILTER_FLAG_SCHEME_REQUIRED - URL must be RFC compliant.
Like http://example

FILTER_FLAG_HOST_REQUIRED - URL must include host name.
Like http://www.example.com

FILTER_FLAG_PATH_REQUIRED - URL must have a path after domain.
Like www.example.com/example1/

FILTER_FLAG_QUERY_REQUIRED - URL must have a query string.
Like "example.php?name=Peter&age=37"

filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED)
filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED)
filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED)
filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED)