You are using laravel-4 template comment syntax to define/set variables which is may be not working with L5.x.

But you can try @php ($p3 = $key['p3'])

OR

@php
$p3 = $key['p3']
@endphp

Above both are same.

Further you go with create own service provider like

• create BladeServiceProvider:

<?php 
//app/Providers/BladeServiceProvider.php
namespace App\Providers;

use Illuminate\Support\ServiceProvider;

class BladeServiceProvider extends ServiceProvider
{
    public function boot()
    {
        /* @datetime($var) */
        \Blade::extend(function($view, $compiler)
        {
            $pattern = $compiler->createOpenMatcher('datetime');

            return preg_replace($pattern, '$1<?php echo $2->format(\'m/d/Y H:i\')); ?>', $view);
        });

        /* @eval($var++) */
        \Blade::extend(function($view)
        {
            return preg_replace('/\@eval\((.+)\)/', '<?php ${1}; ?>', $view);
        });
    }

    public function register()
    {
        //
    }
}

• Register BladeServiceProvider:

<?php
//in config/app.php add
return [

    // ...

    'providers' => [

        // ...

        'App\Providers\BladeServiceProvider',

Clear complied artisan clear-compiled

Assign value to variable @datetime($updated_at)

OR

@eval($var = 1)

Taken reference from: Laravel 5 alternative