(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
stream_set_write_buffer — Sets write file buffering on the given stream
$stream, int $size): int
Sets the buffering for write operations on the given stream
to size bytes.
streamThe file pointer.
size
The number of bytes to buffer. If size
is 0 then write operations are unbuffered. This ensures that all writes
with fwrite() are completed before other processes are
allowed to write to that output stream.
Returns 0 on success, or another value if the request cannot be honored.
示例 #1 stream_set_write_buffer() example
The following example demonstrates how to use stream_set_write_buffer() to create an unbuffered stream.
<?php
$fp = fopen($file, "w");
if ($fp) {
if (stream_set_write_buffer($fp, 0) !== 0) {
// changing the buffering failed
}
fwrite($fp, $output);
fclose($fp);
}
?>Trying to use stream_set_write_buffer on a local file will always fail according to this note from 2003.
http://grokbase.com/t/php/php-internals/0351gp6xtn/stream-set-write-buffer-does-not-work
Example:
$fp = fopen("localfile.txt", "w");
if (stream_set_write_buffer($fp, 0) !== 0) {
// changing the buffering failed is always true on local files
}The stream_set_write_buffer() function has been broken since PHP 4.3.0. As a workaround, I would suggest using a php_user_filter as an output buffer. By using the following class I have measured over 50% performance improvements with scripts that generate large text files by writing them one line at a time:
class my_output_buffer extends php_user_filter
{
protected static $BUFFER_SIZE = 4096;
function onCreate( ) {
$this->bff = [];
$this->len = 0;
return true;
}
public function filter($in, $out, &$consumed, $closing)
{
$rv = PSFS_FEED_ME; /* assume no output */
/* process input */
while ($bucket = stream_bucket_make_writeable($in)) {
/* bucket is too big for the buffer? */
$space = static::$BUFFER_SIZE - $this->len;
if ($bucket->datalen >= $space) {
/* consume data by placing it into internal buffers */
$this->bff[] = substr($bucket->data, 0, $space);
$this->len += $space;
$overflow = substr($bucket->data, $space);
$ovfl_len = $bucket->datalen - $space;
$consumed += $bucket->datalen;
assert($this->len == static::$BUFFER_SIZE);
/* make one big bucket */
$bucket->data = implode('', $this->bff);
$bucket->datalen = static::$BUFFER_SIZE;
stream_bucket_append($out, $bucket);
$rv = PSFS_PASS_ON; /* we have output! */
/* handle overflow */
$this->bff = [$overflow];
$this->len = $ovfl_len;
}
else {
/* consume data by placing it into internal buffers */
$this->bff[] = $bucket->data;
$this->len += $bucket->datalen;
$consumed += $bucket->datalen;
}
}
/* stream is closing and we have data? */
if ($closing && $this->len > 0) {
/* make one last bucket */
$data = implode('', $this->bff);
$bucket = stream_bucket_new($this->stream, $data);
stream_bucket_append($out, $bucket);
$rv = PSFS_PASS_ON; /* we have output! */
/* clear internal buffer */
$this->bff = [];
$this->len = 0;
}
return $rv;
}
}
$fp = fopen('foobar.txt', 'w');
/* enable filtering */
stream_filter_register('output.buffer', 'my_output_buffer');
stream_filter_append($fp, 'output.buffer');
/* a lot of small writes */
for ($i = 0; $i < 10000; $i++) {
fwrite($fp, 'x');
}
fclose($fp);