Why is this not valid PHP? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

PHP: How to chain method on a newly created object?

I started off with this code:

$page = new Page();

$page->replace_tags(...);

$page->output();

I changed the signature of replace_tags to allow method chaining, by returning $this. Why can I still not write it like this?

new Page()->replace_tags(...)->output();

Or this:

(n开发者_运维问答ew Page())->replace_tags(...)->output();

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I think you may need to chain the functions on the class instance:

$page = new Page();

$page->replace_tags(...)->output();

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You need to assign the object to a reference first:

$obj = new Page();
$obj->replace_tags(...)->output();