下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。
| Constant | Description |
|---|---|
| STREAM_FILTER_READ * | Used with stream_filter_append() and stream_filter_prepend() to indicate that the specified filter should only be applied when reading |
| STREAM_FILTER_WRITE * | Used with stream_filter_append() and stream_filter_prepend() to indicate that the specified filter should only be applied when writing |
| STREAM_FILTER_ALL * |
This constant is equivalent to
STREAM_FILTER_READ | STREAM_FILTER_WRITE
|
| PSFS_PASS_ON * | Return Code indicating that the userspace filter returned buckets in $out. |
| PSFS_FEED_ME * | Return Code indicating that the userspace filter did not return buckets in $out (i.e. No data available). |
| PSFS_ERR_FATAL * | Return Code indicating that the userspace filter encountered an unrecoverable error (i.e. Invalid data received). |
| PSFS_FLAG_NORMAL | Regular read/write. |
| PSFS_FLAG_FLUSH_INC | An incremental flush. |
| PSFS_FLAG_FLUSH_CLOSE | Final flush prior to closing. |
| STREAM_USE_PATH | Flag indicating if the stream used the include path. |
| STREAM_REPORT_ERRORS | Flag indicating if the wrapper is responsible for raising errors using trigger_error() during opening of the stream. If this flag is not set, you should not raise any errors. |
| STREAM_CLIENT_ASYNC_CONNECT * | Open client socket asynchronously. This option must be used together with the STREAM_CLIENT_CONNECT flag. Used with stream_socket_client(). |
| STREAM_CLIENT_CONNECT * | Open client socket connection. Client sockets should always include this flag. Used with stream_socket_client(). |
| STREAM_CLIENT_PERSISTENT * | Client socket opened with stream_socket_client() should remain persistent between page loads. |
| STREAM_SERVER_BIND * | Tells a stream created with stream_socket_server() to bind to the specified target. Server sockets should always include this flag. |
| STREAM_SERVER_LISTEN * | Tells a stream created with stream_socket_server() and bound using the STREAM_SERVER_BIND flag to start listening on the socket. Connection-orientated transports (such as TCP) must use this flag, otherwise the server socket will not be enabled. Using this flag for connect-less transports (such as UDP) is an error. |
| STREAM_NOTIFY_RESOLVE * | A remote address required for this stream has been resolved, or the resolution failed. See severity for an indication of which happened. |
| STREAM_NOTIFY_CONNECT | A connection with an external resource has been established. |
| STREAM_NOTIFY_AUTH_REQUIRED | Additional authorization is required to access the specified resource. Typical issued with severity level of STREAM_NOTIFY_SEVERITY_ERR. |
| STREAM_NOTIFY_MIME_TYPE_IS | The mime-type of resource has been identified, refer to message for a description of the discovered type. |
| STREAM_NOTIFY_FILE_SIZE_IS | The size of the resource has been discovered. |
| STREAM_NOTIFY_REDIRECTED | The external resource has redirected the stream to an alternate location. Refer to message. |
| STREAM_NOTIFY_PROGRESS | Indicates current progress of the stream transfer in bytes_transferred and possibly bytes_max as well. |
| STREAM_NOTIFY_COMPLETED * | There is no more data available on the stream. |
| STREAM_NOTIFY_FAILURE | A generic error occurred on the stream, consult message and message_code for details. |
| STREAM_NOTIFY_AUTH_RESULT | Authorization has been completed (with or without success). |
| STREAM_NOTIFY_SEVERITY_INFO | Normal, non-error related, notification. |
| STREAM_NOTIFY_SEVERITY_WARN | Non critical error condition. Processing may continue. |
| STREAM_NOTIFY_SEVERITY_ERR | A critical error occurred. Processing cannot continue. |
| STREAM_IPPROTO_ICMP + | Provides a ICMP socket. |
| STREAM_IPPROTO_IP + | Provides a IP socket. |
| STREAM_IPPROTO_RAW + | Provides a RAW socket. |
| STREAM_IPPROTO_TCP + | Provides a TCP socket. |
| STREAM_IPPROTO_UDP + | Provides a UDP socket. |
| STREAM_PF_INET + | Internet Protocol Version 4 (IPv4). |
| STREAM_PF_INET6 + | Internet Protocol Version 6 (IPv6). |
| STREAM_PF_UNIX + | Unix system internal protocols. |
| STREAM_SOCK_DGRAM + | Provides datagrams, which are connectionless messages (UDP, for example). |
| STREAM_SOCK_RAW + | Provides a raw socket, which provides access to internal network protocols and interfaces. Usually this type of socket is just available to the root user. |
| STREAM_SOCK_RDM + | Provides a RDM (Reliably-delivered messages) socket. |
| STREAM_SOCK_SEQPACKET + | Provides a sequenced packet stream socket. |
| STREAM_SOCK_STREAM + | Provides sequenced, two-way byte streams with a transmission mechanism for out-of-band data (TCP, for example). |
| STREAM_SHUT_RD | Used with stream_socket_shutdown() to disable further receptions. Added in PHP 5.2.1. |
| STREAM_SHUT_WR | Used with stream_socket_shutdown() to disable further transmissions. Added in PHP 5.2.1. |
| STREAM_SHUT_RDWR | Used with stream_socket_shutdown() to disable further receptions and transmissions. Added in PHP 5.2.1. |
| STREAM_CAST_FOR_SELECT | Stream casting, for when stream_select() is calling stream_cast(). |
| STREAM_CAST_AS_STREAM | Stream casting, when stream_cast() is called otherwise (see above). |
Note: The constants marked with * are just available since PHP 5.0.0.
Note: The constants marked with + are available since PHP 5.1.0 and are meant to be used with stream_socket_pair(). Please note that some of these constants might not be available in your system.