XCVIII. Stream functions


Streams were introduced with PHP 4.3.0 as a way of generalizing file, network, data compression, and other opperations which share a common set of functions and uses. In its simplest definition, a stream is a resource object which exhibits streamable behavior. That is, it can be read from or written to in a linear fashion, and may be able to fseek() to an arbitrary locations within the stream.

A wrapper is additional code which tells the stream how to handle specific protocols/encodings. For example, the http wrapper knows how to translate a URL into an HTTP/1.0 request for a file on a remote server. There are many wrappers built into PHP by default (See Appendix I), and additional, custom wrappers may be added either within a PHP script using stream_register_wrapper(), or directly from an extension using the API Reference in Chapter 43. Because any variety of wrapper may be added to PHP, there is no set limit on what can be done with them. To access the list of currently registered wrappers, use stream_get_wrappers().

A filter is a final piece of code which may perform opperations on data as it is being read from or written to a stream. Any number of filters may be stacked onto a stream. Custom filters can be defined in a PHP script using stream_register_filter() or in an extension using the API Reference in Chapter 43. To access the list of currently registered filters, use stream_get_filters().

A stream is referenced as: scheme://target

  • scheme(string) - The name of the wrapper to be used. Examples include: file, http, https, ftp, ftps, compress.zlib, compress.bz2, and php. See Appendix I for a list of PHP builtin wrappers. If no wrapper is specified, the function default is used (typically file://).

  • target - Depends on the wrapper used. For filesystem related streams this is typically a path and filename of the desired file. For network related streams this is typically a hostname, often with a path appended. Again, see Appendix I for a description of targets for builtin streams.


No external libraries are needed to build this extension.


Streams are an integral part of PHP as of version 4.3.0. No steps are required to enable them.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Stream Classes

User designed wrappers can be registered via stream_register_wrapper(), using the class definition shown on that manual page.

class php_user_filter is predefined and is an abstract baseclass for use with user defined filters. See the manual page for stream_register_filter() for details on implementing user defined filters.

Predefined Constants

STREAM_USE_PATHFlag indicating if the stream used the include path.
STREAM_REPORT_ERRORSFlag 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 Errors

As with any file or socket related function, an opperation on a stream may fail for a variety of normal reasons (i.e.: Unable to connect to remote host, file not found, etc...). A stream related call may also fail because the desired stream is not registered on the running system. See the array returned by stream_get_wrappers() for a list of streams supported by your installation of PHP. As with most PHP internal functions if a failure occours an E_WARNING message will be generated describing the nature of the error.


Example 1. Using file_get_contents() to retrieve data from multiple sources

/* Read local file from /home/bar */
$localfile = file_get_contents("/home/bar/foo.txt");

/* Identical to above, explicitly naming FILE scheme */
$localfile = file_get_contents("file:///home/bar/foo.txt");

/* Read remote file from www.example.com using HTTP */
$httpfile  = file_get_contents("http://www.example.com/foo.txt");

/* Read remote file from www.example.com using HTTPS */
$httpsfile = file_get_contents("https://www.example.com/foo.txt");

/* Read remote file from ftp.example.com using FTP */
$ftpfile   = file_get_contents("ftp://user:pass@ftp.example.com/foo.txt");

/* Read remote file from ftp.example.com using FTPS */
$ftpsfile  = file_get_contents("ftps://user:pass@ftp.example.com/foo.txt");

Example 2. Making a POST request to an https server

/* Send POST request to https://secure.example.com/form_action.php
 * Include form elements named "foo" and "bar" with dummy values

$sock = fsockopen("ssl://secure.example.com", 443, $errno, $errstr, 30);
if (!$sock) die("$errstr ($errno)\n";

$data = "foo=" . urlencode("Value for Foo") . "&bar=" . urlencode("Value for Bar");

fputs($sock, "POST /form_action.php HTTP/1.0\r\n");
fputs($sock, "Host: secure.example.com\r\n");
fputs($sock, "Content-type: application/x-www-url-encoded\r\n");
fputs($sock, "Content-length: " . strlen($data) . "\r\n");
fputs($sock, "Accept: */*\r\n");
fputs($sock, "\r\n");
fputs($sock, "$data\r\n");
fputs($sock, "\r\n");

$headers = "";
while ($str = trim(fgets($sock, 4096)))
  $headers .= "$str\n";

print "\n";

$body = "";
while (!feof($sock))
  $body .= fgets($sock, 4096);


Example 3. Writting data to a compressed file

/* Create a compressed file containing an arbitrarty string
 * File can be read back using compress.zlib stream or just
 * decompressed from the command line using 'gzip -d foo-bar.txt.gz'
$fp = fopen("compress.zlib://foo-bar.txt.gz","wb");
if (!$fp) die("Unable to create file.");

fwrite($fp, "This is a test.\n");


Table of Contents
stream_context_create -- Create a streams context
stream_context_get_options -- Retrieve options for a stream/wrapper/context
stream_context_set_option -- Sets an option for a stream/wrapper/context
stream_context_set_params -- Set parameters for a stream/wrapper/context
stream_filter_append -- Attach a filter to a stream.
stream_filter_prepend -- Attach a filter to a stream.
stream_get_filters -- Retrieve list of registered filters
stream_get_meta_data -- Retrieves header/meta data from streams/file pointers
stream_get_wrappers -- Retrieve list of registered streams
stream_register_filter -- Register a stream filter implemented as a PHP class derived from php_user_filter
stream_register_wrapper -- Register a URL wrapper implemented as a PHP class
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
stream_set_blocking -- Set blocking/non-blocking mode on a stream
stream_set_timeout -- Set timeout period on a stream
stream_set_write_buffer -- Sets file buffering on the given stream