数组foreach引发的小问题

<code><span>$arr1</span> = [ <span>1</span>, <span>2</span>, <span>3</span>, <span>4</span>, <span>5</span> ];
<span>$arr2</span> = [ <span>'a'</span>, <span>'b'</span>, <span>'c'</span>, <span>'d'</span>, <span>'e'</span> ];
<span>$arr3</span> = [];
<span>foreach</span> (<span>$arr1</span><span>as</span> & <span>$v</span>){
    <span>$v</span> += <span>10</span>; 

}

<span>foreach</span> (<span>$arr2</span><span>as</span><span>$k</span> => <span>$v</span>){
    <span>//举例</span><span>$v</span> = <span>$v</span> . <span>$arr1</span>[ <span>$k</span> ];
    <span>$arr3</span>[ <span>$k</span> ] = <span>$v</span>;
}
<span>echo</span> implode(<span>', '</span>, <span>$arr1</span>) . <span>"\n"</span> . implode(<span>', '</span>, <span>$arr2</span>) . <span>"\n"</span> . implode(<span>', '</span>, <span>$arr3</span>);</code>

<code><span>11</span>, <span>12</span>, <span>13</span>, <span>14</span>, ee
<span>a</span>, b, c, d, e
a11, b12, c13, d14, ee</code>

<code><span>11</span>, <span>12</span>, <span>13</span>, <span>14</span>, <span>15</span><span>a</span>, b, c, d, e
a11, b12, c13, d14, e15</code>