PHP, Structures and Functions Acting on a Disk system


<?php

bool stream_context_set_params ( res $context , 
                                                     arr $params )


where,

$context = The stream or context to 
                                  apply the parameters too
                                                                                
$params = An array of parameters to set, should be 
                 an associative array of the structure:
                  
                  $params['paramname'] = "paramvalue"
                  
?>

$context

The stream or context to apply the parameters too.

A STREAM WRAPPER is an abstraction of a file system that allows PHP to use the same set of methods to access both local files and remote resources.

Provide a facility for managing and querying user-defined STREAM WRAPPERS.

In this system the registered REGISTERED STREAM WRAPPERS can be seen in the below table.

PROTOCOLS	MEANING
file://	LOCAL File System
http://	URL HTTP
ftp://	URL FTP
php://	I/O streams
zlib://	Data Compression stream
data://	DATA (RFC-2397)
glob://	Find Filenames
phar://	PHP Archive
ssh2://	Secure Shell 2
rar://	RAR
ogg://	Audio
expect://	Interaction of stream processes
ed48

$params

SUPPORTED PARAMETERS
Parameters	Purpose
notification	Name of user-defined callback function to be called whenever a stream triggers a notification. Only supported for http:// and ftp:// stream wrappers.
options	Array of options as in context options and parameters.
ed48

Accessing http:// or https://

Allows read-only access to files/resources via HTTP 1.0, using the HTTP GET method.

A Host: header is sent with the request to handle name-based virtual hosts.

If you have configured a user_agent string using your php.ini file or the stream context, it will also be included in the request.

Attribute	Supported
Restricted by: allow_url_fopen	Yes
Allows Reading	Yes
Allows Writing	No
Allows Appending	No
Allows Simultaneous Reading and Writing	N/A
Supports stat	No
Supports unlink	No
Supports rename	No
Supports mkdir	No
Supports rmdir	No
ed48

HTTPS is only supported when the openssl extension is enabled.

Examlpes:

http://example.com
http://example.com/file.php?var1=val1&var2=val2
http://user:password@example.com

https://example.com
https://example.com/file.php?var1=val1&var2=val2
https://user:password@example.com


<?php

Context options for http:// and https:// transports. 

str method

    GET, POST, or any other HTTP method
    supported by the remote server.

    Defaults to GET.
    
    
arr or str header

    Additional headers to be sent during request.
    Values in this option will override other values,
    (such as User-agent:, Host:, and Authentication:).
    
    
str user_agent

    Value to send with User-Agent: header.
    This value will only be used 
    if user-agent is not specified 
    in the header context option above.

    By default the user_agent php.ini setting is used.
    
    
str content

    Additional data to be sent after the headers.
    Typically used with POST or PUT requests.
    
    
str proxy

    URI specifying address of proxy server.
    
    
bool request_fulluri

    When set to TRUE, the entire URI 
    will be used when constructing the request.
    (HTTP/1.0). 
    While this is a non-standard request format,
    some proxy servers require it.

    Defaults to FALSE.
    
    
int follow_location

    Follow Location header redirects. Set to 0 to disable.

    Defaults to 1.
    
    
int max_redirects

    The max number of redirects to follow.
    Value 1 or less means 
    that no redirects are followed.

    Defaults to 20.
    
    
float protocol_version

    HTTP protocol version.

    Defaults to 1.0.           

?>

Accessing ftp:// or ftps://

Allows read access to existing files and creation of new files via FTP.

If the server does not support passive mode ftp, the connection will fail.

You can open files for either reading or writing, but not both simultaneously.

If the remote file already exists on the ftp server and you attempt to open it for writing but have not specified the context option overwrite, the connection will fail.

If you need to overwrite existing files over ftp, specify the overwrite option in the context and open the file for writing.

Attribute	Supported
Restricted by: allow_url_fopen	Yes
Allows Reading	Yes
Allows Writing	Yes (new files/existing files with overwrite
Allows Appending	Yes
Allows Simultaneous Reading and Writing	No
Supports stat	filesize, filetype, file_exists, is_file and is_dir elements only. As of PHP 5.1.0: filemtime.
Supports unlink	Yes
Supports rename	Yes
Supports mkdir	Yes
Supports rmdir	Yes
ed48

Examlpes:

ftp://example.com/pub/file.txt
ftp://user:password@example.com/pub/file.txt

ftps://example.com/pub/file.txt
ftps://user:password@example.com/pub/file.txt


<?php

Context options for ftp:// and ftps:// transports. 

bool overwrite

    Allow overwriting of already existing files
    on remote server. 
    Applies to write mode, (uploading), only.

    Defaults to FALSE.
    
    
int resume_pos

    File offset at which to begin transfer. 
    Applies to read mode, (downloading), only.

    Defaults to 0 (Beginning of File).
    
    
str proxy

    Proxy FTP request via http proxy server.
    Applies to file read operations only.           

?>

EXERCISE


<?php

define('PA1W', 'file://' . __DIR__ . '/adds/love.txt');

echo PA1W . "<br><br>";

$path01 = PA1W;

$fl01 = fopen($path01,"r");
//  MUST EXIST

$opts01 = [ 'https' => [ 'method'=>"POST",
          'header' => "Accept-language: en"] ]; 

$cntxt01 = stream_context_set_params($fl01, $opts01);


if($cntxt01 == TRUE)
{
echo '<br>STREAM CONTEXT IS SET AS EXPECTED<br><br>';
}
else
{
echo '<br>STREAM CONTEXT IS NOT SET AS EXPECTED<br><br>';
}

?>

RESULT

STREAM CONTEXT IS SET AS EXPECTED

EXERCISE


<?php

define('PA2W', 'file://' . __DIR__ . '/adds'); 

$path02 = PA2W;

echo $path02 . "<br><br>"; 

$fl02 = fopen($path02 . '/sw7.jpg' ,"r");
//  MUST EXIST

$opts02 = [ 'https' => [ 'method'=>"POST",
          'header' => "Accept-language: en"] ]; 

$cntxt02 = stream_context_set_params($fl02, $opts02);


if($cntxt02 == TRUE)
{
echo '<br>STREAM CONTEXT IS SET AS EXPECTED<br><br>';
}
else
{
echo '<br>STREAM CONTEXT IS NOT SET AS EXPECTED<br><br>';
}

?>

RESULT

STREAM CONTEXT IS SET AS EXPECTED

EXERCISE


<?php

define('PA3W', 'file://' . __DIR__ . '/adds');  

echo PA3W . "<br><br>"; 

$path03 = PA3W;

$fl03 = @fopen($path03 . '/sw7.png' ,"r");
//  DOES NOT EXIST

$opts03 = [ 'https' => [ 'method'=>"POST",
          'header' => "Accept-language: en"] ]; 

$cntxt03 = stream_context_set_params($fl03, $opts03);

if($cntxt03 == TRUE)
{
echo '<br>STREAM CONTEXT IS SET AS EXPECTED<br><br>';
}
else
{
echo '<br>STREAM CONTEXT IS NOT SET AS EXPECTED<br><br>';
}

?>