php_stream_read() reads up to count
bytes of data from stream and copies them into the
buffer buf.
php_stream_read() returns the number of bytes that were read successfully. There is no distinction between a failed read or an end-of-file condition - use php_stream_eof() to test for an EOF.
The internal position of the stream is advanced by the number of bytes that were read, so that subsequent reads will continue reading from that point.
If less than count bytes are available to be read, this
call will block (or wait) until the required number are available, depending on the
blocking status of the stream. By default, a stream is opened in blocking mode.
When reading from regular files, the blocking mode will not usually make any
difference: when the stream reaches the EOF
php_stream_read() will return a value less than
count, and 0 on subsequent reads.