array_change_key_case ----返回字符串键名全为小写或大写的数组
说明：
array_change_key_case() 将 input 数组中的所有键名改为全小写或大写。改变是根据后一个选项 case 参数来进行的。可以在这里用两个常量，CASE_UPPER 和 CASE_LOWER。默认值是 CASE_LOWER。本函数不改变数字索引。
Example #1 array_change_key_case() 例子
<span style="color: rgb(0,0,0)"><font face="NSimsun"><span style="color: rgb(0,0,187)"><?php <br/>
$input_array </span><span style="color: rgb(0,119,0)">= array(</span><span style="color: rgb(221,0,0)">"FirSt" </span><span style="color: rgb(0,119,0)">=> </span><span style="color: rgb(0,0,187)">1</span><span style="color: rgb(0,119,0)">, </span><span style="color: rgb(221,0,0)">"SecOnd" </span><span style="color: rgb(0,119,0)">=> </span><span style="color: rgb(0,0,187)">4</span></font><font face="NSimsun"><span style="color: rgb(0,119,0)">);<br>
</span><span style="color: rgb(0,0,187)">print_r</span><span style="color: rgb(0,119,0)">(</span><span style="color: rgb(0,0,187)">array_change_key_case</span><span style="color: rgb(0,119,0)">(</span><span style="color: rgb(0,0,187)">$input_array</span><span style="color: rgb(0,119,0)">, </span><span style="color: rgb(0,0,187)">CASE_UPPER</span></font><font face="NSimsun"><span style="color: rgb(0,119,0)">));<br>
</span><span style="color: rgb(0,0,187)">?></span>
</font></span>
上例将输出：
Array<br>(<br> [FIRST] => 1<br> [SECOND] => 4<br>)<br>
如果一个数组中的多个键名经过本函数后变成一样的话（例如 "keY" 和 "kEY"），最后一个值将覆盖其它的值。
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