stream_set_write_buffer

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

stream_set_write_buffer — Sets write file buffering on the given stream

Description

stream_set_write_buffer(resource $stream, int $size): int

Sets the buffering for write operations on the given stream to size bytes.

Parameters

stream: The 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.

Return Values

Returns 0 on success, or another value if the request cannot be honored.

Examples

Example #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);
}
?>

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User Contributed Notes 2 notes

down

MOX ¶

2 years ago

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);