PHP数组关于数字键名的有关问题
PHP数组关于数字键名的问题
以下是对PHP数组数字键名的几点总结:
键名长度只能在 int 长度范围内,超过int 范围后将会出现覆盖等混乱情况
在键名长度为 int 范围内存取值时,PHP会强制将数字键名转换为 int 数值型
数字键名长度大于19位时,将变成 0
键名正常长度时,字符串或数值类型一样
$i = 126545165;$arr['126545165'] = 'abc';$arr[126545165] = 'uio';var_dump($arr);echo '<br>';var_dump(isset($arr[$i]));

长度超过整型时,键名混乱
$i = 12312312312312;$arr['1000000000147483649'] = 'abc';$arr[1000000000147483649] = 'uio';var_dump($arr);echo '<br>';var_dump(isset($arr[$i]));
长度超过20位时,键名将变成 0
$i = 123123123123123123123123123123;var_dump($i);echo '<br>';$arr[123123123123123123123123123123] = 'abc';$arr[strval(123123123123123123123123123123)] = 'abc';var_dump($arr);echo '<br>';var_dump(isset($arr[$i]));echo '<br>';var_dump(isset($arr[strval($i)]));echo '<br>';var_dump(array_keys($arr));

将变量直接作为键名存取,结果又有不同
$i = 123123123123123;var_dump($i);echo '<br>';$arr[$i] = 'abc';$arr[strval($i)] = 'abc';var_dump($arr);echo '<br>';var_dump(isset($arr[$i]));echo '<br>';var_dump(isset($arr[strval($i)]));echo '<br>';var_dump(array_keys($arr));

从上面的几种测试来看:
如果键名为数字,且范围在 int 以内,字符串或者 int 不会对存取有什么影响
如果长度大于 int 时会自动转化为 float ,再转换进行存取出现各种混乱情况,甚至直接变成 0,所以最好是统一转换为 string 类型
$i = 123123123123123123123123123123;$j = '123123123123123123123123123123';$arr1[strval($i)] = 'abc';$arr2[$j] = 'abc';var_dump($arr1);echo '<br>';var_dump($arr2);
所以在动态操作 PHP 数组时,如果不能确定键名是否会出现数字或者长度大于 int ,则统一将键名 strval 转换为 字符串来操作最为稳妥

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