============================
 getValueFrom
============================

For interoperability with other systems it is interesting to have the possibility to use dynamic values in the xml configuration file.

For example: One system is used to create a new feature with passes an attibute proprety in the url.

To allow this kind of interoperability it is possible to replace a fixed value in some xml nodes with a special <getValueFrom> tag that allows to get a value from any php variable table.


Use
----

.. code-block:: xml

    <!-- fixed option -->
    <option>value</option> 
    
    <!-- dynamique value -->
    <option>
        <getValueFrom>$_REQUEST[param]</getValueFrom>
    </option> 
    <option>
        <getValueFrom>$_POST[firstname] $_POST[lastname]</getValueFrom>
    </option>
    <option>
        <getValueFrom>$GLOBALS[lang]</getValueFrom>
    </option>
    <option>
        <getValueFrom>$SESSION[username]</getValueFrom>
    </option>
    <option>
        <getValueFrom>He is now" . date() . "</getValueFrom>
    </option>
    
Implementation
---------------
The values set in getValueFrom tag are put into a string and are evaluated with the 'eval' php function.

Php code can then be used to return the desired value dynamically.

**P.S :** All widgets that use nodes loaded with *getObjectFromNode* are automatically compatible with *getValueFrom* (e.g. featurepanel_form fields)
    
Sample
--------


* Use 'getValueFrom' with the stylemap option of the `map <./list/Map.html#layer-options>`_ widget to colorize features with a attribute value equal to that passed along in the url.

    .. code-block:: xml
    
        <stylemap>
            <renderers>
                <renderer>
                    <renderintent>default</renderintent>
                    <style>
                        <fillcolor>${getColor}</fillcolor>
                        <strokecolor>${getColor}</strokecolor> 
                        <context>
                            <functions>                                            
                                <fidegualfunction>
                                    <name>getColor</name>
                                    <egual>
                                        <getValueFrom>$_REQUEST[id]</getValueFrom>   <!-- <<<<<<<<<<<<< Here <<<<<<<<<<<<  --> 
                                    </egual>
                                    <result>#FF00FF</result>
                                    <defaultresult>#00FFFF</defaultresult>                                            
                                </fidegualfunction>
                            </functions> 
                        </context>
                    </style>
                </renderer>
            </renderers>
        </stylemap>
        

* Use 'getValueFrom' with the 'editfeature_create' and 'featurepanel_form' widgets to add features with an attribute value obtained from the url.

    .. code-block:: xml
    
        <editfeature_create>
            <name>CreateDumpingSite</name>
            <options>
                <geometrytype>Polygon</geometrytype>
                <featurepanel>FeaturePanel1</featurepanel>
            </options>
        </editfeature_create>
        
        <featurepanel_form>
            <name>FeaturePanel1</name>
            <options>
                <inwindow>true</inwindow>
                <windowoffset>
                    <left>100</left>
                </windowoffset>
                <windowoptions>
                    <title>
                        <en_US>Dumping Site</en_US>
                        <fr_CA>Site de déversement</fr_CA> 
                    </title>
                    <autoScroll>false</autoScroll>
                </windowoptions>
                <defaults>
                    <width>100</width>
                </defaults>
                <fields>
                    <field>
                        <name>dumpingid</name>
                        <xtype>displayfield</xtype>                 
                        <value>
                            <getValueFrom>$_REQUEST[id]</getValueFrom>  <!-- <<<<<<<<<<<<< Here <<<<<<<<<<<<  -->
                        </value>
                    </field> 
                </fields>
            </options>
        </featurepanel_form>