Description
int 
stream_set_write_buffer ( resource stream, int buffer )
     Output using fwrite() is normally buffered at
     8K.  This means that if there are two processes wanting to write
     to the same output stream (a file), each is paused after 8K of
     data to allow the other to write.
     stream_set_write_buffer()
     sets the buffering for write operations on the given filepointer
     stream to buffer bytes.
     If buffer 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.
    
     The function returns 0 on success, or EOF if the request cannot
     be honored.
    
     The following example demonstrates how to use
     stream_set_write_buffer() to create an unbuffered stream.
     
Example 1. stream_set_write_buffer() example 
<?php $fp = fopen($file, "w"); if ($fp) {   stream_set_write_buffer($fp, 0);   fwrite($fp, $output);   fclose($fp); } ?>
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     See also
     fopen() and
     fwrite().