how to append one array to another array in php

 ((data.userDetails.profile_picture === null) ||(data.userDetails.profile_picture===undefined))? picture ='<div><img src="http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/nebula_brown.png"' :
          picture = '<img src="'+data.userDetails.profile_picture+ '"/>';