(PHP 4 >= 4.3.0)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
Descriptionint stream_select ( resource &read, resource &write, resource &except, int tv_sec [, int tv_usec])
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.
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 0, stream_select() will not wait for data - instead it will return immediately, indicating the current status of the streams. If tv_sec is NULL stream_select() can block indefinitely, returning only when an event on one of the watched streams occurs (or if a signal interrupts the system call).
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 FALSE is returned and a warning raised (this can happen if the system call is interrupted by an incoming signal).
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 example checks to see if data has arrived for reading on either $stream1 or $stream2. Since the timeout value is 0 it will return immediately:
See also stream_set_blocking()