How to implement hook_theme in drupal 7?

Question

I created a new drupal 7 theme and trying to implement hook_theme at template.php like this:

function mytheme_theme($existing, $type, $theme, $path){
    return array(
        'mytheme_header'=>array(
            'template'=>'header',
            'path'=>$path.'/templates',
            'type'=>'theme',
        ),
    );
}

then I placed header.tpl.php into templates directory and cleared all caches, and call theme function:

theme('mytheme_header', $vars);

and header.tpl.php likes this:

<?php
fb('calling header template');//the function of FirePHP to output debug info
print '<div>Header</div>';
//...

I check Firebug and it get the info 'calling header template', it mean it had called header.tpl.php, but it didn't print the html code. What's wrong with my code?

Solution

Try to add the variables array in hook_theme

function mytheme_theme($existing, $type, $theme, $path){
    return array(
        'mytheme_header' => array(
            'template' => 'header',
            'path' => $path . '/templates',
            'type' => 'theme',
            'variables' => array(
                'title' => NULL,
                'some_text' => NULL,
            ),
        ),
    );
}

In your header.tpl.php file:

<h1><?php print $title; ?></h1>
<p><?php print $some_text; ?></p>

Then, print it out like this:

$vars = array();
$vars['title'] = "This is a title";
$vars['some_text'] = "Some text...";
print theme('mytheme_header', $vars);

Comments

[Clive]

arguments was renamed to variables in Drupal 7

[solomon_wzs]

It was not the problem of variables. I debug with FirePHP and I found that It had called header.tpl.php but it didn't print any html code.

[solomon_wzs]

I'm sorry, I called theme($hook, $vars), but I should call print theme($hook, $vars).