How worsk $this->l('sth')

[walter_alf]

Hello,

I need to add a couple of phrases in PHP file and I use function l, like this: 

$sth = $this->l('Office furniture').

But where can I add translating to 'Office furniture'? For example if I use {l s='some sentence'} in *.tpl files, I can modify translating in diffrent languages for 'some sentence' in presta admin panel in Localization->Translating -> Modify translating and there is 'some sentence'. When I use $this->l I can't find translating to my phrases anything.

I have Prestashop in version 1.5.4.1

 

Best regards