为什么在设置之前声明数组（php）？ [重复]

I dont know why people declare array before loops and etc..:

$new= array();      // <----- why this is needed ?
foreach($something as $v){
    $new[] = $v;
}

Why to declare the array before setting its value? (In other languages, i.e. C# and JAVA it is needed, but why in PHP?)

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You're not setting its value, you're pushing a new element onto the array. But there needs to be an empty array to push onto.