Create context-lifetime.md

docs/context-lifetime.md

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+# PHP context lifetime
+
+PHP context usually terminates with the PHP script execution. It is the standard behavior of PHP. However, we can utilize PeachPie and Blazor to save the context on a client side to save the application state.
+
+> An example can be seen in [https://github.com/peachpiecompiler/peachpie-blazor/tree/dev/docs/src/Tests/Examples/AllTogether](https://github.com/peachpiecompiler/peachpie-blazor/tree/dev/docs/src/Tests/Examples/AllTogether), where we utilize the persistent context for saving data from many parts of the application representing different PHP scripts.
+
+You will change the context lifetime of the provider by setting the `ContextLifetime` parameter to  `SessionLifetime.Persistant`. When a client navigates to another PHP script, the context of this script is the same as the previous one. 
+
+> The current implementation doesn't support more than one context at a time. So when there are two instances of the provider with different `ContextLifetime`, the context persistency will not work.
+
+```razor
+<PhpScriptProvider ContextLifetime="@SessionLifetime.Persistant" Type="@PhpScriptProviderType.ScriptProvider">
+    <Navigating>
+        <p>Navigating</p>
+    </Navigating>
+    <NotFound>
+        <p>Not found</p>
+    </NotFound>
+</PhpScriptProvider>
+```