AJAX and PHP

Chapter 8
save() and undo() are helper functions used for editing rows. The save function saves the
original product values, which are loaded back to the grid by undo if the user changes her or his
mind about the change and clicks the Cancel link.
Row updating functionality is supported by the updateRow function, which is called when the Update
link is clicked. updateRow() makes an asynchronous call to the server, specifying the new product
values, which are composed into the query string using the createUpdateUrl helper function:
// update one row in the grid if the connection is clear
function updateRow(grid, productId)
{
// continue only if the XMLHttpRequest object isn't busy
if (xmlHttp && (xmlHttp.readyState == 4 || xmlHttp.readyState == 0))
{
var query = feedGridUrl + "?action=UPDATE_ROW&id=" + productId +
"&" + createUpdateUrl(grid);
xmlHttp.open("GET", query, true);
xmlHttp.onreadystatechange = handleUpdatingRow;
xmlHttp.send(null);
}
}
The handleUpdatingRow callback function has the responsibility to ensure that the product change
is performed successfully, in which case it disables edit mode for the row, or displays an error
message if an error happened on the server side:
// continue only if HTTP status is "OK"
if(xmlHttp.status == 200)
{
// read the response
response = xmlHttp.responseText;
// server error?
if (response.indexOf("ERRNO") >= 0
|| response.indexOf("error") >= 0
|| response.length == 0)
alert(response.length == 0 ? "Server serror." : response);
// if everything went well, cancel edit mode
else
editId(editableId, false);
}
The technique for displaying the error was implemented in other exercises as well. If the server
returned a specific error message, that message is displayed to the user. If PHP is configured not to
output errors, the response from the server will be void, in which case we simply display a generic
error message.
Summary
In this chapter you have implemented already familiar AJAX techniques to build a data grid. You
have met XSL, which allows implementing very powerful architectures where the server side of
your application doesn't need to deal with presentation.
Having XSL deal with formatting the data to be displayed to your visitors is the professional way
to deal with these kinds of tasks, and if you are serious about web development, it is recommended
to learn XSL well. Beware; this will be time and energy consuming, but in the end the effort will
be well worth it.
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