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We shall create an Xajax application to validate an input field in a form. The input form takes data to add a catalog entry to the database table Catalog. As a user begins to enter data in the input field Catalog Id, a XMLHttpRequest is sent to the server to validate the Catalog Id value added.

If the Catalog Id is not already defined in the database, a message "Catalog Id is Valid" gets displayed. If the Catalog Id is already defined in the database, a message "Catalog Id is not Valid" gets displayed, the Create Catalog button gets disabled and field values for the Catalog Id get added to the form.

The xajax PHP object performs the function of an intermediary between the client application and the server. In the Xajax application PHP script create a xajax object.

$xajax = new xajax();

The server side processing is performed by PHP functions. Create PHP functions validateCatalogId($formValues) and updateCatalog($formValues). Both these functions take a formValues parameter.

function validateCatalogId($formValues){}
function updateCatalog($formValues){}

Register the PHP functions with the xajax object using the registerFunction() method. The xajax object creates wrapper functions for the PHP functions that may be invoked from a PHP script or an input form event handler.

$xajax->registerFunction("validateCatalogId");
$xajax->registerFunction("updateCatalog");

Xajax generates asynchronous wrapper functions for the registered PHP functions. A wrapper function name uses the format phpfunction. Variable phpfunction is a server-side PHP function for which a wrapper function is to be defined. Xajax provides asynchronous form processing with the getFormValues(string formId) method. Using the getFormValues() method, an array of form field values may be submitted as an argument to a xajax asynchronous function.

Sections of a form may also be submitted instead of the complete form with the getFormValues(string formID ,boolean submitDisabledElements, string prefix]) function. The prefix parameter specifies that only form elements starting with that prefix should be submitted. Boolean parameter submitDisabledElementsspecifies if disabled elements are to be submitted. PHP functions validateCatalogId and updateCatalog define a parameter for an array of form field values. Before a XMLHttpRequestis initiated, specify the xajax object to handle requests with the processRequests() function.

$xajax->processRequests();

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