©
このドキュメントでは、 php中国語ネットマニュアル リリース
Note:
The functions in this chapter are for use in the PHP source code and are not PHP functions. Information on userland stream functions can be found in the Stream Reference.
The PHP Streams API introduces a unified approach to the handling of files and sockets in PHP extension. Using a single API with standard functions for common operations, the streams API allows your extension to access files, sockets, URLs, memory and script-defined objects. Streams is a run-time extensible API that allows dynamically loaded modules (and scripts!) to register new streams.
The aim of the Streams API is to make it comfortable for developers to open files, URLs and other streamable data sources with a unified API that is easy to understand. The API is more or less based on the ANSI C stdio family of functions (with identical semantics for most of the main functions), so C programmers will have a feeling of familiarity with streams.
The streams API operates on a couple of different levels: at the base level, the API defines php_stream objects to represent streamable data sources. On a slightly higher level, the API defines php_stream_wrapper objects which "wrap" around the lower level API to provide support for retrieving data and meta-data from URLs. An additional context parameter, accepted by most stream creation functions, is passed to the wrapper's stream_opener method to fine-tune the behavior of the wrapper.
Any stream, once opened, can also have any number of filters applied to it, which process data as it is read from/written to the stream.
Streams can be cast (converted) into other types of file-handles, so that they can be used with third-party libraries without a great deal of trouble. This allows those libraries to access data directly from URL sources. If your system has the fopencookie() or funopen() function, you can even pass any PHP stream to any library that uses ANSI stdio!
Using streams is very much like using ANSI stdio functions. The main difference is in how you obtain the stream handle to begin with. In most cases, you will use php_stream_open_wrapper() to obtain the stream handle. This function works very much like fopen, as can be seen from the example below:
Example #1 simple stream example that displays the PHP home page
php_stream * stream = php_stream_open_wrapper("http://www.php.net", "rb", REPORT_ERRORS, NULL); if (stream) { while(!php_stream_eof(stream)) { char buf[1024]; if (php_stream_gets(stream, buf, sizeof(buf))) { printf(buf); } else { break; } } php_stream_close(stream); }
The table below shows the Streams equivalents of the more common ANSI stdio functions. Unless noted otherwise, the semantics of the functions are identical.
ANSI Stdio Function | PHP Streams Function | Notes |
---|---|---|
fopen | php_stream_open_wrapper | Streams includes additional parameters |
fclose | php_stream_close | |
fgets | php_stream_gets | |
fread | php_stream_read | The nmemb parameter is assumed to have a value of 1, so the prototype looks more like read(2) |
fwrite | php_stream_write | The nmemb parameter is assumed to have a value of 1, so the prototype looks more like write(2) |
fseek | php_stream_seek | |
ftell | php_stream_tell | |
rewind | php_stream_rewind | |
feof | php_stream_eof | |
fgetc | php_stream_getc | |
fputc | php_stream_putc | |
fflush | php_stream_flush | |
puts | php_stream_puts | Same semantics as puts, NOT fputs |
fstat | php_stream_stat | Streams has a richer stat structure |
All streams are registered as resources when they are created. This ensures that they will be properly cleaned up even if there is some fatal error. All of the filesystem functions in PHP operate on streams resources - that means that your extensions can accept regular PHP file pointers as parameters to, and return streams from their functions. The streams API makes this process as painless as possible:
Example #2 How to accept a stream as a parameter
PHP_FUNCTION(example_write_hello) { zval *zstream; php_stream *stream; if (FAILURE == zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r", &zstream)) return; php_stream_from_zval(stream, &zstream); php_stream_write(stream, "hello\n"); RETURN_TRUE(); }
Example #3 How to return a stream from a function
PHP_FUNCTION(example_open_php_home_page) { php_stream *stream; stream = php_stream_open_wrapper("http://www.php.net", "rb", REPORT_ERRORS, NULL); php_stream_to_zval(stream, return_value); }
Since streams are automatically cleaned up, it's tempting to think that we can get away with being sloppy programmers and not bother to close the streams when we are done with them. Although such an approach might work, it is not a good idea for a number of reasons: streams hold locks on system resources while they are open, so leaving a file open after you have finished with it could prevent other processes from accessing it. If a script deals with a large number of files, the accumulation of the resources used, both in terms of memory and the sheer number of open files, can cause web server requests to fail. Sounds bad, doesn't it? The streams API includes some magic that helps you to keep your code clean - if a stream is not closed by your code when it should be, you will find some helpful debugging information in you web server error log.
Note: Always use a debug build of PHP when developing an extension (--enable-debug when running configure), as a lot of effort has been made to warn you about memory and stream leaks.
In some cases, it is useful to keep a stream open for the duration of a request, to act as a log or trace file for example. Writing the code to safely clean up such a stream is not difficult, but it's several lines of code that are not strictly needed. To save yourself the trouble of writing the code, you can mark a stream as being OK for auto cleanup. What this means is that the streams API will not emit a warning when it is time to auto-cleanup a stream. To do this, you can use php_stream_auto_cleanup() .
These constants affect the operation of stream factory functions.
IGNORE_PATH
USE_PATH
IGNORE_URL
IGNORE_URL_WIN
ENFORCE_SAFE_MODE
REPORT_ERRORS
STREAM_MUST_SEEK
Note: If the requested resource is network based, this flag will cause the opener to block until the whole contents have been downloaded.
STREAM_WILL_CAST
[#1] armand at nl dot envida dot net [2003-09-11 14:05:18]
To have your extension ignore the open_basedir restrictions that may be set, use
STREAM_DISABLE_OPENBASEDIR
I'm not sure why this option is left out of the documentation,
there are valid and legit uses for this option.