Returns the time the file was last modified, or FALSE in case of an error. The time is returned as a Unix timestamp, which is suitable for the date() function.
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提示: As of PHP 5.0.0 this function can also be used with some URL wrappers. Refer to 附錄 M for a listing of which wrappers support stat() family of functionality.
This function returns the time when the data blocks of a file were being written to, that is, the time when the content of the file was changed.
See also filectime(), stat(), touch(), and getlastmod().