Php/docs/function.bindec
bindec
(PHP 4, PHP 5, PHP 7)
bindec — 二进制转换为十进制
说明
bindec
( string $binary_string
) : number
返回
binary_string 参数所表示的二进制数的十进制等价值。
bindec() 将一个二进制数转换成 integer，或者出于大小的需要，转换为 float 类型。
bindec() 将所有的
binary_string 值解释为无符号整数。这是由于
bindec() 函数将其最高有效位视为数量级而非符号位。
参数
binary_string- 要转换的二进制字符串
Warning 参数必须为字符串。使用其他数据类型会导致不可预知的结果。
返回值
binary_string 的十进制数值
更新日志
| 版本 | 说明 |
|---|---|
| 4.1.0 | 本函数如今可以转换超过程序运行平台中
integer 类型最大值的数，此时其值会返回为 float 类型。 |
范例
Example #1 bindec() 例子
<?phpecho bindec('110011') . "\n";echo bindec('000110011') . "\n";echo bindec('111');?>
以上例程会输出：
51 51 7
Example #2 bindec() 将输入解读为无符号整数
<?php/* * The lesson from this example is in the output * rather than the PHP code itself. */$magnitude_lower = pow(2, (PHP_INT_SIZE * 8) - 2);p($magnitude_lower - 1);p($magnitude_lower, 'See the rollover? Watch it next time around...');p(PHP_INT_MAX, 'PHP_INT_MAX');p(~PHP_INT_MAX, 'interpreted to be one more than PHP_INT_MAX');if (PHP_INT_SIZE == 4) { $note = 'interpreted to be the largest unsigned integer';} else { $note = 'interpreted to be the largest unsigned integer (18446744073709551615) but skewed by float precision';}p(-1, $note);function p($input, $note = ) { echo "input: $input\n"; $format = '%0' . (PHP_INT_SIZE * 8) . 'b'; $bin = sprintf($format, $input); echo "binary: $bin\n"; ini_set('precision', 20); // For readability on 64 bit boxes. $dec = bindec($bin); echo 'bindec(): ' . $dec . "\n"; if ($note) { echo "NOTE: $note\n"; } echo "\n";}?>
以上例程在 32 位机器上的输出:
input: 1073741823 binary: 00111111111111111111111111111111 bindec(): 1073741823 input: 1073741824 binary: 01000000000000000000000000000000 bindec(): 1073741824 NOTE: See the rollover? Watch it next time around... input: 2147483647 binary: 01111111111111111111111111111111 bindec(): 2147483647 NOTE: PHP_INT_MAX input: -2147483648 binary: 10000000000000000000000000000000 bindec(): 2147483648 NOTE: interpreted to be one more than PHP_INT_MAX input: -1 binary: 11111111111111111111111111111111 bindec(): 4294967295 NOTE: interpreted to be the largest unsigned integer
以上例程在 64 位机器上的输出:
input: 4611686018427387903
binary: 0011111111111111111111111111111111111111111111111111111111111111
bindec(): 4611686018427387903
input: 4611686018427387904
binary: 0100000000000000000000000000000000000000000000000000000000000000
bindec(): 4611686018427387904
NOTE: See the rollover? Watch it next time around...
input: 9223372036854775807
binary: 0111111111111111111111111111111111111111111111111111111111111111
bindec(): 9223372036854775807
NOTE: PHP_INT_MAX
input: -9223372036854775808
binary: 1000000000000000000000000000000000000000000000000000000000000000
bindec(): 9223372036854775808
NOTE: interpreted to be one more than PHP_INT_MAX
input: -1
binary: 1111111111111111111111111111111111111111111111111111111111111111
bindec(): 18446744073709551616
NOTE: interpreted to be the largest unsigned integer
(18446744073709551615) but skewed by float precision
