I'm looking for the most efficient way to write the contents of the PHP input stream to disk, without using much of the memory that is granted to the PHP script. For example, if the max file size that can be uploaded is 1 GB but PHP only has 32 MB of memory.
define('MAX_FILE_LEN', 1073741824); // 1 GB in bytes
$hSource = fopen('php://input', 'r');
$hDest = fopen(UPLOADS_DIR.'/'.$MyTempName.'.tmp', 'w');
fwrite($hDest, fread($hSource, MAX_FILE_LEN));
fclose($hDest);
fclose($hSource);
Does fread inside an fwrite like the above code shows mean that the entire file will be loaded into memory?
For doing the opposite (writing a file to the output stream), PHP offers a function called fpassthru which I believe does not hold the contents of the file in the PHP script's memory.
I'm looking for something similar but in reverse (writing from input stream to file). Thank you for any assistance you can give.
Yep - fread
used in that way would read up to 1 GB into a string first, and then write that back out via fwrite
. PHP just isn't smart enough to create a memory-efficient pipe for you.
I would try something akin to the following:
$hSource = fopen('php://input', 'r');
$hDest = fopen(UPLOADS_DIR . '/' . $MyTempName . '.tmp', 'w');
while (!feof($hSource)) {
/*
* I'm going to read in 1K chunks. You could make this
* larger, but as a rule of thumb I'd keep it to 1/4 of
* your php memory_limit.
*/
$chunk = fread($hSource, 1024);
fwrite($hDest, $chunk);
}
fclose($hSource);
fclose($hDest);
If you wanted to be really picky, you could also unset($chunk);
within the loop after fwrite
to absolutely ensure that PHP frees up the memory - but that shouldn't be necessary, as the next loop will overwrite whatever memory is being used by $chunk
at that time.
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