php 이상한 현상이 발생하는데 답변 부탁드립니다

<span><?php
</span><span >$aBU </span><span >= </span><span >array </span><span >(
</span><span ></span><span >array </span><span >( </span><span >'id' </span><span >=> </span><span>'0'</span><span>, </span><span>)</span><span>,
</span><span></span><span>array </span><span>( </span><span>'id' </span><span>=> </span><span>'1'</span><span>, </span><span>)</span><span>,
</span><span></span><span>array </span><span>( </span><span>'id' </span><span>=> </span><span>'2'</span><span>, </span><span>)</span><span>,
</span><span></span><span>array </span><span>( </span><span>'id' </span><span>=> </span><span>'3'</span><span>, </span><span>)</span><span>,
</span><span>)</span><span>;
</span><span>echo </span><span>"<h3></span><span color: background-color:>原来数据</span><span></h3>"</span><span>;
</span><span>print_r(</span><span>$aBU</span><span>)</span><span>;
</span><span>echo </span><span>"<hr />"</span><span>;
</span><span></span><span>foreach</span><span>(</span><span>$aBU </span><span>as  </span><span>&</span><span>$bu</span><span>){
</span><span></span><span>$bu</span><span>[</span><span>'dept'</span><span>] = rand(</span><span>100</span><span>, </span><span>999</span><span>)</span><span>;
</span><span>}
</span><span>//unset($bu);
</span><span>echo </span><span>"<h3></span><span color: background-color:>加入</span><span>dept</span><span color: background-color:>后</span><span></h3>"</span><span>;
</span><span>print_r(</span><span>$aBU</span><span>)</span><span>;
</span><span>echo </span><span>"<hr />"</span><span>;
</span><span></span><span></span><span>echo </span><span>"<h3></span><span color: background-color:>重新遍历</span><span></h3>"</span><span>;
</span><span>foreach</span><span>(</span><span>$aBU </span><span>as </span><span>$key </span><span>=> </span><span>$bu</span><span>){
</span><span>    print_r(</span><span>$bu</span><span>)</span><span>;
</span><span></span><span>echo </span><span>"<br />"</span><span>;
</span><span>}</span>