Heim  >  Artikel  >  php教程  >  [PHP]array

[PHP]array

WBOY
WBOYOriginal
2016-06-06 19:49:262017Durchsuche

--------------------------------------------------------------------------------------------------------- /* |----------------------------------------------------------|array_map();将回调函数作用到给定数组的单元上|array_column();快速实现:

---------------------------------------------------------------------------------------------------------

<span>/*</span><span>
|----------------------------------------------------------
|array_map();将回调函数作用到给定数组的单元上
|array_column();快速实现:将二维数组转为一维数组
|----------------------------------------------------------
</span><span>*/<br></span>

array array_column ( array $input , mixed $column_key [, mixed $index_key ] );

返回input数组中值为column_key的列; 如果指定了可选参数index_key,返回的数组中 对应键 为input数组值index_key对应的值。

 

<span>例一:<br>$records</span> = <span>array</span><span>(
    </span><span>array</span><span>(
        </span>'id' => 2135,
        'first_name' => 'John',
        'last_name' => 'Doe',<span>
    )</span>,
    <span>array</span><span>(
        </span>'id' => 3245,
        'first_name' => 'Sally',
        'last_name' => 'Smith',<span>
    )</span>,
    <span>array</span><span>(
        </span>'id' => 5342,
        'first_name' => 'Jane',
        'last_name' => 'Jones',<span>
    )</span>,
    <span>array</span><span>(
        </span>'id' => 5623,
        'first_name' => 'Peter',
        'last_name' => 'Doe',<span>
    )
);
 
</span><span>$first_names</span> = array_column(<span>$records</span>, 'first_name'<span>);
</span><span>print_r</span>(<span>$first_names</span>);<br>/*<br>输出:
Array
(
    [0] => John
    [1] => Sally
    [2] => Jane
    [3] => Peter
)
*/

<span>例二:<br>$last_names</span> = array_column(<span>$records</span>, 'last_name', 'id'<span>);
</span><span>print_r</span>(<span>$last_names</span>);<br>/*<br>输出:
Array
(
    [2135] => Doe
    [3245] => Smith
    [5342] => Jones
    [5623] => Doe
)
*/

 

<span>当没有array_column()函数情况下,

</span><span>//</span><span>使用array_map()实现例一:</span>
<span>$a</span> = <span>array_map</span>(<span>function</span>(<span>$element</span>){  <span>//</span><span>$records作为参数传入回调函数</span>
  <span>return</span> <span>$element</span>['last_name'];   <span>//</span><span>返回数组元素值的last_name对应值</span><span>
}</span>, <span>$records</span>);              <span>//</span><span>array_map返回数组,相当于把每个$element['last_name']存入新数组,所以是新建的索引</span>

 

<span>//</span><span>使用foreach实现例一:</span>
<span>foreach</span>(<span>$records</span> <span>as</span> <span>$v</span><span>)
{
    </span><span>$b</span>[] = <span>$v</span>['last_name'<span>];
}</span>

 

<span>//</span><span>使用foreach实现例二:</span>
<span>$c</span> = <span>array</span><span>();
</span><span>foreach</span>(<span>$records</span> <span>as</span> <span>$k</span>=><span>$v</span><span>)
{
 </span><span>$c</span> += <span>array</span>(<span>$v</span>['id']=><span>$v</span>['last_name']); <span>//</span><span>使用+运算符, 以追加的形式(不改变原数组索引), 合并组装的数组</span><span>
}                         </span><span>//</span><span>若使用array_merge,数字键名将被重新编号</span>

 

在取出的多条数据中,典型的二维数组,如果需要使用数据中单一的 值与值 对应的情况,array_column()即可完成,但是面对较复杂的数组结构,foreach才能让你更灵活,不过优先使用系统函数总是首选的。

 

Link: http://www.cnblogs.com/farwish/p/3855831.html

@黑眼诗人 

Stellungnahme:
Der Inhalt dieses Artikels wird freiwillig von Internetnutzern beigesteuert und das Urheberrecht liegt beim ursprünglichen Autor. Diese Website übernimmt keine entsprechende rechtliche Verantwortung. Wenn Sie Inhalte finden, bei denen der Verdacht eines Plagiats oder einer Rechtsverletzung besteht, wenden Sie sich bitte an admin@php.cn