Source

File: wp-admin/includes/file.php

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;
}