xslt_set_scheme

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cchittleborough at cluemail dot com
13-Sep-2004 09:36


Here's some useful information I found in the PHP 4.3.4 source (in the file ext/xslt/README.XSLT-BACKENDS):



void xslt_set_scheme_handlers(resource processor, array handlers)



Registers the scheme handlers for the document (aka XPath handlers), given a XSLT processor resource (allocated by xslt_create()) and an array in the following format:

 

    array(

       "get_all" => function,

       "open"    => function,

       "get"      => function,

       "put"      => function,

       "close"    => function

    )

 

Where function is either a function name or an array in the following format:

 

    array(&$obj, "method")



Note:  You do not need to handle the array(&$obj, method") syntax by yourself as this is handled in the C call_xslt_function() library function (and more specifically, Zend's call_user_function_ex() function.



Note:  The given array does not need to contain all of the different scheme handler elements (although it can), but it only needs to conform to the "handler" => "function" format described above.



Each of the individual scheme handler functions called are in the formats below:

 

    string    get_all(resource processor, string scheme, string rest)

    resource open(resource processor, string scheme, string rest)

    int       get(resource processor, resource fp, string &data)

    int       put(resource processor, resource fp, string data)

    void      close(resource processor, resource fp)

ohlesbeauxjours at yahoo dot fr
21-Mar-2003 03:49


xslt_set_scheme_handlers is a powerful feature, derived from the Sablotron engine, which can help in various situations.



Briefly, it allows you to call any kind of PHP instruction, during the treatment of a stylesheet, through the XSLT document() function.



For example, here is an implementation of the "file_exists()" PHP function :



// Definition of the handler :

function mySchemeHandler($processor, $scheme, $rest) {

  $rest=substr($rest,1);    // to remove the first / automatically added by the engine

  if($scheme == 'file_exists')

    return '<?xml version="1.0" encoding="UTF-8"?><root>'.(file_exists($rest) ? "true" : "false")."</root>";

    // result is embedded in a small xml string

}



// Initialisation of the handler (the "get_all"  should be work in most cases) :

$SchemeHandlerArray = array();

$SchemeHandlerArray["get_all"] = "mySchemeHandler";



// Start the engine :

$params = array();

$xh = xslt_create();

xslt_set_scheme_handlers($xh,$SchemeHandlerArray);

$result = xslt_process($xh,"myFile.xml","myFile.xsl",NULL,array(),$params);

xslt_free($xh);

echo $result;



Then, inside the stylesheet, you can test whether a certain file exists with :

<xsl:if test="document('file_exists:anotherXMLfile.xml)/root='true'">

 < !-- bla bla bla -->

</xsl:if>



So finally, the principle is simple :

-    you define a scheme (here, I called it "file_exists")

-    you write the action associated to that scheme (in the mySchemeHandler function)

-    you embed the (probable) results in an XML string, that you return.

-    and in the stylesheet, you check : document('myPersonalURIscheme:myXPath')



You can imagine many other uses for the mySchemeHandler() function.



My framework is : PHP 4.2.3, Sablotron version 0.96, and Expat 1.95.5

Please note that some older version of PHP might require an additionnal parameter :

 mySchemeHandler($processor,$scheme,$rest,&$buffer)

and you place your XML in $buffer, instead of returning it with return().



Baptiste

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xslt_set_scheme_handlers

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