Any example code ?
My guess is that your $form variable holds some kind of form object which as a method to output its content... something like
Code:
$form = new FormObject;
$form->setAction('/some/url');
$form->addField('text', 'name');
$form->render();
But in any case, the content of the form must be printed to the output with an 'echo' or 'print' statement (in the example above, that would happen somewhere in the render() method of the form object.
The only other thing I can think of is that you have seen the use of some sort of 'echo/print' shortcut in an html template. Something like
Code:
[some html]
<?php
$form = '<form action"....................">all the content</form>';
?>
[some more html]
<?=$form?> <= this is a shortcut to <?php echo $form ?>