Attempts to clear the opcode cache for an individual PHP file.

This function can be called safely without having to check the file extension
or availability of the OPcache extension.

Whether or not invalidation is possible is cached to improve performance.

function wp_opcache_invalidate( $filepath, $force = false ) {
	static $can_invalidate = null;

	/*
	 * Check to see if WordPress is able to run `opcache_invalidate()` or not, and cache the value.
	 *
	 * First, check to see if the function is available to call, then if the host has restricted
	 * the ability to run the function to avoid a PHP warning.
	 *
	 * `opcache.restrict_api` can specify the path for files allowed to call `opcache_invalidate()`.
	 *
	 * If the host has this set, check whether the path in `opcache.restrict_api` matches
	 * the beginning of the path of the origin file.
	 *
	 * `$_SERVER['SCRIPT_FILENAME']` approximates the origin file's path, but `realpath()`
	 * is necessary because `SCRIPT_FILENAME` can be a relative path when run from CLI.
	 *
	 * For more details, see:
	 * - https://www.php.net/manual/en/opcache.configuration.php
	 * - https://www.php.net/manual/en/reserved.variables.server.php
	 * - https://core.trac.wordpress.org/ticket/36455
	 */
	if ( null === $can_invalidate
		&& function_exists( 'opcache_invalidate' )
		&& ( ! ini_get( 'opcache.restrict_api' )
			|| stripos( realpath( $_SERVER['SCRIPT_FILENAME'] ), ini_get( 'opcache.restrict_api' ) ) === 0 )
	) {
		$can_invalidate = true;
	}

	// If invalidation is not available, return early.
	if ( ! $can_invalidate ) {
		return false;
	}

	// Verify that file to be invalidated has a PHP extension.
	if ( '.php' !== strtolower( substr( $filepath, -4 ) ) ) {
		return false;
	}

	/**
	 * Filters whether to invalidate a file from the opcode cache.
	 *
	 * @since 5.5.0
	 *
	 * @param bool   $will_invalidate Whether WordPress will invalidate `$filepath`. Default true.
	 * @param string $filepath        The path to the PHP file to invalidate.
	 */
	if ( apply_filters( 'wp_opcache_invalidate_file', true, $filepath ) ) {
		return opcache_invalidate( $filepath, $force );
	}

	return false;
}