set NegativeCampaignCriterion for location using adword api php

how to set exclude location for campaign. i tried to found out it . i found this 

$negativeCriterion = new \NegativeCampaignCriterion();

 $negativeCriterion->campaignId = $result->value[0]->id;

 $negativeCriterion->criterion = $location;

but i cannot understand how to pass location here. could you explain with example ?

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