src/class-wp-register.php
protected static function is_modified_file( $filepath ) {

		$actual = filemtime( $filepath );

		$last = isset( self::$files[ $filepath ] ) ? self::$files[ $filepath ] : 0;

		if ( $actual !== $last ) {

			self::$files[ $filepath ] = $actual;

			self::$changes = true;

			return self::$changes;
		}

		return false;
	}
protected static function is_modified_file( $filepath ) {

		$actual = filemtime( $filepath );

		$last = isset( self::$files[ $filepath ] ) ? self::$files[ $filepath ] : 0;

		if ( $actual !== $last ) {

			self::$files[ $filepath ] = $actual;

			self::$changes = true;

			return self::$changes;
		}

		return false;
	}
Check if the file was modified.

@since 1.0.4

@param string $filepath → path of the file.

@return boolean