(PHP 4 >= 4.3.2, PHP 5, PHP 7, PHP 8)
streamWrapper::stream_read — Read from stream
This method is called in response to fread() and fgets().
注意:
Remember to update the read/write position of the stream (by the number of bytes that were successfully read).
countHow many bytes of data from the current position should be returned.
If there are less than count
bytes available, as many as are available should be returned.
If no more data is available, an empty string should be returned.
To signal that reading failed, false should be returned.
调用此方法失败将给出
E_WARNING（未实现）。
注意:
If the return value is longer then
countanE_WARNINGerror will be emitted, and excess data will be lost.
注意:
streamWrapper::stream_eof() is called directly after calling streamWrapper::stream_read() to check if EOF has been reached. If not implemented, EOF is assumed.
When reading the whole file (for example, with file_get_contents()), PHP will call streamWrapper::stream_read() followed by streamWrapper::stream_eof() in a loop but as long as streamWrapper::stream_read() returns a non-empty string, the return value of streamWrapper::stream_eof() is ignored.