Returns a string containing the version of the currently running PHP parser or extension.
An optional extension name.
Returns the current PHP version as a string. If a string argument is provided for extension parameter, phpversion returns the version of that extension, or false if there is no version information associated or the extension isn't enabled.
This information is also available in the predefined constant PHP_VERSION. More versioning information is available using the PHP_VERSION_* constants.
|extension is nullable now.