It might not be precisely what you want, but using the aforementioned second parameter you could do this:

<title>Website Name : @yield('page_title', 'Tagline goes here')</title>

EDIT: After I posted I saw your revision tobysommer

Both sounds like great suggestions but they aren't direct solution to my question.

I don't want to put a default value in case there's none, I need to know how to check if it returns something.

Still, I wasn't aware of that second parameter for @yield() so thanks a lot, I'm sure this will me anyways :)

I have encountered this similar problem before.

I end up with View composer

	class MetaComposer{

		public function compose($view)
		{
			
			if ( ! empty($view['title']) )
			{
			    $view['title'] .= ' | '.$site_title;
			}
			else
			{
			    $view['title'] = $site_title;
			}
			
			return $view;
		}
	}

You can use this in your view:

@if (array_key_exists('mySection', View::getSections()))
foo
@else
bar
@endif

I came up with a slightly icky solution to this:

@if ($__env->yieldContent('title')
    @yield('title')
    | My Site
@else
   Welcome to my wonderful website!
@endif

I'm using this helper function in my Laravel 5 apps:

/**
 * Checks whether a section has been captured yet.
 *
 * @param  string  $section
 * @return bool
 */
function content_for($section)
{
    return array_key_exists($section, app('view')->getSections());
}

Too much work, simply use:

@if (View::hasSection('something'))
do something
@else
do nothing
@endif

P/S: Please have a look into "vendor/laravel/framework/src/Illuminate/View/Factory.php"

It's even simpler now. Use the @hasSection directive:

<title>
    @hasSection('title')
        @yield('title') - App Name
    @else
        App Name
    @endif
</title>

Wow. Thank you, adriaanzon! Is there any way to use @hasSection in a ternary?

I have been doing this for about 2 years now and this is my implementation.

<title>@yield('body.title', 'default title') | Always here</title>

Then in my templates used

@section('body.title', 'Contact Us')