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Digg stream_select
Runs the equivalent of the select() system call on the given
arrays of streams with a timeout specified by tv_sec and tv_usec
(PHP 4 >= 4.3.0, PHP 5)
The stream_select() function accepts arrays of streams and waits for them to change status. Its operation is equivalent to that of the socket_select() function except in that it acts on streams. The streams listed in the read array will be watched to see if characters become available for reading (more precisely, to see if a read will not block - in particular, a stream resource is also ready on end-of-file, in which case an fread() will return a zero length string). The streams listed in the write array will be watched to see if a write will not block. The streams listed in the except array will be watched for high priority exceptional ("out-of-band") data arriving.
Note:
When stream_select() returns, the arrays read, write and except are modified to indicate which stream resource(s) actually changed status.
The tv_sec and tv_usec
together form the timeout parameter,
tv_sec specifies the number of seconds while
tv_usec the number of microseconds.
The timeout is an upper bound on the amount of time
that stream_select() will wait before it returns.
If tv_sec and tv_usec are
both set to
On success stream_select() returns the number of
stream resources contained in the modified arrays, which may be zero if
the timeout expires before anything interesting happens. On error
Warning:
Using a timeout value of
It is much better to specify a timeout value of a few seconds, although
if you need to be checking and running other code concurrently, using a
timeout value of at least Remember that the timeout value is the maximum time that will elapse; stream_select() will return as soon as the requested streams are ready for use.
You do not need to pass every array to
stream_select(). You can leave it out and use an
empty array or
This example checks to see if data has arrived for reading on either
$stream1 or $stream2.
Since the timeout value is <?php
Note:
Due to a limitation in the current Zend Engine it is not possible to pass a
constant modifier like <?php
Note:
Be sure to use the <?php
Note:
If you read/write to a stream returned in the arrays be aware that they do not necessarily read/write the full amount of data you have requested. Be prepared to even only be able to read/write a single byte.
Note:
Windows compatibility: stream_select() used on a pipe returned from proc_open() may cause data loss under Windows 98.
Use of stream_select() on
file descriptors returned by proc_open() will fail
and return See also stream_set_blocking(). Code Examples / Notes » stream_selectben
You can key on file descriptors just fine by casting them to an int or a string, which returns what you would expect.
mbaynton
The documentation states that: You do not need to pass every array to stream_select(). You can leave it out and use an empty array or NULL instead. Also do not forget that those arrays are passed by reference and will be modified after stream_select() returns. This appears to be incorrect, at least in PHP 5.1.6, because PHP sees these parameters are passed by reference and thus insists on a bona fide variable for the reference to refer to: Fatal error: Only variables can be passed by reference is what you get if you pass NULL or anything else literally. maxdamantus
Simple stream_select wrapper.. Returns the first stream in the array, and sets parameter 2 to the key (So that it is easy to identify what received data): <?php function select($array, &$vkey, $timeout=0){ $select = array(); $null = NULL; foreach($array as $key => $sock){ $x = count($select); $select[$x] = $sock; $keys[$x] = $key; } if(stream_select($select, $null, $null, $timeout)){ foreach($keys as $key){ if($array[$key] == $select[0]){ $vkey = $key; return($select[0]); } } } } $streams = array("foo" => $stream_one, "bar" => $stream_two); // Create an array of two (already existant) streams. if($new = select($streams, $key, 60)){ //Sets $new to the resource that next gets new data, and $key to either "foo", or "bar", depending which one it is. echo $key.":".stream_get_line($new, 2048)."\n"; } ?> phpdoc
Please note that, on return, the key of "read" will be zero based, serially numbered according to the streams for which there is read data ready only. In other words, if you want to know which of the original streams placed in "read" is ready, there is no immediate way of knowing that. If you want to know which of the original stream is which, you can either use "==", or possibly set a reverse map array, in which the stream is the key, and the key to the original "read" array is the data. maartenwolzak
Note that you should change the calctimeout function below to divide the outcome by 1.000.000 otherwise you'll be waiting for two years instead of one minute for the socket to timeout... <?php // The function to calculate the timeout function calctimeout($maxtime, $starttime) { return ($maxtime - ((microtime(true) - $starttime) * 1000000))/1000000; } ?> aidan
Note that contrary to what the previous poster said, one is not able to use a stream resource as a key for an array. Rather, if you want to know which socket you are dealing with, consider using code similar to this: <?php $sockets = array("sock_1" => $sock1, "sock_2" => $sock2, "sock_3" => $sock_3); $read = $write = $error = $sockets; $num = stream_select($read, $write, $error, 10); if ($n > 0) { foreach ($read as $r) { $key = array_search($r, $sockets); // $key will be "sock_1", "sock_2", "sock_3", etc. } } ?> Hope that helps someone out there! bluej100@gmail
@mbaynton at gmail dot com A handy syntactic trick: <?php $r = Array($stream1, $stream2); stream_select($r, $w = null, $x = null, 1337); ?> I've seen it recommended elsewhere in the documentation for clarifying magic arguments so maintainers don't have to go check the function itself, but it also solves your problem here. |
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stream_bucket_append stream_bucket_make_writeable stream_bucket_new stream_bucket_prepend stream_context_create stream_context_get_default stream_context_get_options stream_context_set_option stream_context_set_params stream_copy_to_stream stream_encoding stream_filter_append stream_filter_prepend stream_filter_register stream_filter_remove stream_get_contents stream_get_filters stream_get_line stream_get_meta_data stream_get_transports stream_get_wrappers stream_register_wrapper stream_resolve_include_path stream_select stream_set_blocking stream_set_timeout stream_set_write_buffer stream_socket_accept stream_socket_client stream_socket_enable_crypto stream_socket_get_name stream_socket_pair stream_socket_recvfrom stream_socket_sendto stream_socket_server stream_socket_shutdown stream_wrapper_register stream_wrapper_restore stream_wrapper_unregister |
