问题
In PHP, i will write (create) the file using file_put_contents($filename, $data);
It is ok, but i want to detect the finish event of process.
Currently, the page is showing loading status.
This is currently the way i can know it is finish or not.
I want to detect with the code.
回答1:
This is a blocking, I/O call, so it finishes when the function call returns. The return value is the number of bytes written (upon success).
回答2:
It puts everything on hold until it's over
So you could use something like this to determine when it has finished writing the file.
echo "The file's contents are now being written, please wait.";
file_put_contents($filename, $data);
echo "The file's contents have been written.";
回答3:
Retrieve the Content-Length header from the remote location first. You can use get_headers to do that. Like so:
$headers = get_headers($url, 1);
echo "To download: " . $headers['Content-Length'] . " bytes.<br />";
来源：https://stackoverflow.com/questions/6085524/how-to-detect-the-size-of-file-before-download-while-remote-downloading