Create php-js-interoperability.md

docs/php-js-interoperability.md

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+# PHP JavaScript interoperability
+
+The interoperability is interesting part of the integration. We are able to call JS from PHP and vice versa.
+
+## Calling JavaScript
+
+When we want to call JS function, we just use prepared methods `CallJsVoid` or `CallJs`, which takes the method names, method parameters  and calls the desired function for us.
+
+```php
+<?php
+    CallJsVoid("window.alert", "Hello from PHP script.");
+?>
+```
+
+## Calling PHP
+
+We can also call PHP function, when there is an instance of `PhpScriptProvider` or `PhpComponent`. We just call `window.php.callPHP`, which takes the function name and its parameter as JSON structure.
+
+We can see an example of usage in the example below.
+
+```php
+<p>Click and look at console output</p>
+<button onclick="window.php.callPHP('CallPHP', { name : 'Bon', surname: 'Jovi'});">PHP</button>
+<?php
+
+function CallPHP($data)
+{
+    $json = json_decode($data); 
+
+	echo "Hello ". $json->name . " " . $json->surname .  " from PHP\n";
+}
+?>
+```