PHP - 如何设置数组的每个索引的默认值

I am having trouble dealing with arrays. PHP throws an error if I access an index of an array which does not exists and It is getting difficult conditioning for every index. Is there any way I could set default value for every index of an array so even if I access a non-existent index of an array then it returns the default set value?I am having trouble dealing with arrays. PHP th