is there any built-in function or api to convert a result array into a json

[adrianmak]

For example, I find all pages with template name ABCDE

$items = $this->pages->find("template=ABCDE");
 foreach ($items as $item) {
                echo "<pre>" . var_dump($item) . "</pre>";
             }

}

I var dump for each item, it has many other irrelevant data.

[kongondo]

'those many other irrelevant' data are actually very relevant ..Your find returns several Page objects (OK, could be one if only one hit found) each with lots of properties about the object. Because of this, var_dump() is not very helpful. What data exactly do you need from your find? Is that what you want to encode to json? Then you could do something like this...

$myItems = array();
$items = $this->pages->find("template=ABCDE");
foreach ($items as $item) $myItems[] = array('id'=> $item->id, 'title' => $item->title);
$myItemsJSON = json_encode($myItems);//

[adrian]

You also might find this module by soma very useful:

http://modules.processwire.com/modules/chrome-php-logger/

It logs lots of useful info to the console, including: "current page with all its fields and their value and field settings"

I think this will be the easiest option for what I think you want.