In web services, creating a zip of extensive files for download can be resource-intensive. The conventional approach involves creating a temporary zip file and echoing it to the user or saving it to disk. However, this method leads to issues such as:
An alternative approach is to leverage the streaming capabilities of the Linux command-line tool, zip. By employing a pipeline command like ls -1 | zip -@ - | cat > file.zip, zip can operate in streaming mode, resulting in a minimal memory footprint. A pipe in this context functions as a buffer; when the buffer is filled, the operating system temporarily halts the writing program. This ensures that zip operates at a pace that aligns with the writing speed of the accompanying program.
To achieve the same streaming mechanism on a LAMP stack using PHP, you can utilize the popen() or proc_open() functions to execute the zip command. The stdout from the command can then be retrieved as a PHP stream. By combining these techniques, the following code snippet demonstrates how to stream a zip file to the user as it's being created:
header('Content-Type: application/octet-stream'); header('Content-disposition: attachment; filename="file.zip"'); $fp = popen('zip -r - file1 file2 file3', 'r'); $bufsize = 8192; $buff = ''; while(!feof($fp)) { $buff = fread($fp, $bufsize); echo $buff; } pclose($fp);
This code streams the zip file directly to the client without the need for temporary storage or excessive memory consumption. It effectively emulates the functionality of the cat command in the bash snippet.
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