All phrases that used on your apps should be defined before using. The below instructions will help you:
How to to define?

Add a phrase.json file on under your app directory, this file contains all phrase in your app.

Example:

{ 
     "Var Name" : "", 
     "var_name" : "Message Text"
}

There are 2 ways to define translation:

The easiest way

Put phrase on key, put blank on value (of json).

Example:

{ 
     "Manage Video" : "" 
}

Use:

<?php
echo _p("Manage Video");

// print Manage Video

var_name define:

Put var_name on key, put phrase on value (of json).

Example:

{ 
     "manage_video" : "Manage Video" 
}

Usage

<?php
echo _p("manage_video");

// print Manage Video

<?php
_p('var_name', $attr);

Within phpFox template .html.php file:

{_p var="var_name" $attr}

Within phpFox template *.html file:

{{ _p("var_name", $arrt) }}

Within JavaScript file

oTranslations['var_name', context]

Translate a phrase with context variables

{
    "total_people_liked_this_blog" : "{total} people liked this blog
}

Usage

<?php
echo _p("total_people_liked_this_blog", ["total" => 5]);

Result: 5 people liked this blog