Debugging

DomTemplate is small, but when a larger page has many binds it is still helpful to know where a given value came from.

That is where data-bind-debug comes in.

Enable bind debugging in the HTML

Add data-bind-debug to a scope element:

<section data-bind-debug>
	<h1 data-bind:text="name">Guest</h1>
	<p><a data-bind:href="emailLink" data-bind:text="email">guest@example.com</a></p>
</section>

Now when a bind happens within that scope, DomTemplate records the source file and line number on the affected elements.

What the output looks like

After binding, an element might end up with:

<h1 data-bind-debug="text=app/Controller.php:10">Cody</h1>

Or for multiple properties:

<a data-bind-debug="text=app/Controller.php:10,href=app/Controller.php:10" href="mailto:cody@example.com">cody@example.com</a>

This makes it much easier to answer the question, "which bind call wrote this?"

Scope behaviour

Only elements inside a data-bind-debug scope collect debug entries.

That means we can add it to a single section of the page while leaving the rest untouched, or even just add the debug attribute to the single element we want to inspect.

Cleanup behaviour

cleanupDocument() removes an empty data-bind-debug marker from scope elements, but it keeps populated debug attributes on elements that actually recorded bind information, so we get useful debug output without leaking empty marker attributes.

Tables and lists

Debug information also works with generated content such as:

• list items produced by bindList
• table cells produced by bindTable

That is particularly handy when the final nodes did not even exist in the original HTML.

Selector context errors

Another useful debugging improvement is selector-based bind contexts.

If we write:

$binder->bindKeyValue("name", "Cody", "#missing");

and the selector does not match, DomTemplate throws ContextElementNotFoundException instead of a low-level type error.

That usually gives us a much faster route to the actual mistake in the template or controller code.

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This is the end of the guide. Read the API reference for the method and exception cheat sheet.