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php数组合并，php数组

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Release： 2016-06-13 08:43:27

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php数组合并，php数组

php的array，和java是有很大差距的，虽然php的弱类型的设计可能会被很多java、C++的程序员诟病，但是我觉得在数组容器的设计上，php走的比java和C++都要远。

java的容器设计除了不彻底的问题，其允许存在类C++的数组的存在，是java语言本身唯一一处不满足一切皆对象的存在。

实际上容器的存在，本身是要降低一定的效率的，可是如果过分强调效率，为什么不干脆使用机器码呢？所以我不太喜欢那些拿php容器设计走的过分远的观点。

众所周知，php的array本身是map。

对于普通数组而言，实际上其内部结构是：

$arr1=array(1,2,3,4,5);
print_r($arr1,1);
 
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

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而对于我们通常理解的map而言，php内部是这么实现的：

<span>$arr2</span>=<span>array</span>('c'=>1,'y'=>2,'m'=>3<span>);
</span><span>print_r</span>(<span>$arr2</span>,1<span>);

 </span><span>Array</span><span>
(
    [c] </span>=> 1<span>
    [y] </span>=> 2<span>
    [m] </span>=> 3<span>
)</span>

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对于数组合并而言，你可以认为php使用了类似于C++的重载功能，重载了加号：

 <span>print_r</span>(<span>$arr1</span>+<span>$arr2</span>,1<span>);
</span><span>Array</span><span>
(
    [</span>0] => 1<span>
    [</span>1] => 2<span>
    [</span>2] => 3<span>
    [</span>3] => 4<span>
    [</span>4] => 5<span>
    [c] </span>=> 1<span>
    [y] </span>=> 2<span>
    [m] </span>=> 3<span>
)</span>

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这种数组合并很方便于你从头遍历这个数组，因为在很多时候你不会采用随机访问的方式使用数组，而是从头遍历到结尾。

不过，这里，你容易忽略的一个问题是，array本质就是map。如果两个数组有相同键的时候，是很容易被你忽略的：

<span>$arr1</span>=<span>array</span>(1,2,3,4,5<span>);
</span><span>$arr2</span>=<span>array</span>(7,8,9<span>);
</span><span>$arr3</span>=<span>array</span>('1'=>'c','2'=>'y','3'=>'m','4'=>'z','5'=>'a'<span>); <br /><br /></span><span>print_r</span>(<span>$arr1</span>+<span>$arr2</span>,1<span>);<br /> </span><span>print_r</span>(<span>$arr1</span>+<span>$arr3</span>,1<span>); <br /><br /></span><span>Array</span><span> ( <br />     [</span>0] => 1<span> <br />     [</span>1] => 2<span> <br />     [</span>2] => 3<span> <br />     [</span>3] => 4<span> <br />     [</span>4] => 5

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<em id="__mceDel"><span>)
 
 </span><span>Array</span><span>
(
    [</span>0] => 1<span>
    [</span>1] => 2<span>
    [</span>2] => 3<span>
    [</span>3] => 4<span>
    [</span>4] => 5<br />    [5] => a</em>

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