--------------------------------------------------------------------------------------------------------- /* |----------------------------------------------------------|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