php - Why should substr be used to intercept the content obtained through file_get_contents?

Question

A problem recorded before, the complete code cannot be found.... It is not clear now why $iTime needs to be obtained by intercepting the file content, please take a look, thank you.

Answer 1

This must be written for specific situations.
My guess is that it is a file cache of data. The first 11 digits store the expired timestamp, and the next 11 digits store the data content. By getting the first 11 digits to get the timestamp, we can determine whether the cache has expired, and then process it.
It is used in specific situations and is not universal, but it is still a way to cache files.