php中的抽象方法和抽象类
122
2024-01-10
(PHP 4, PHP 5)
bindec — 二进制转换为十进制
说明
number bindec ( string$binary_string
)
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
<?php
echo 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: $inputn";
$format = '%0' . (PHP_INT_SIZE * 8) . 'b';
$bin = sprintf($format, $input);
echo "binary: $binn";
ini_set('precision', 20); // For readability on 64 bit boxes.
$dec = bindec($bin);
echo 'bindec(): ' . $dec . "n";
if ($note) {
echo "NOTE: $noten";
}
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
参见
decbin() - 十进制转换为二进制 octdec() - 八进制转换为十进制 hexdec() - 十六进制转换为十进制 base_convert() - 在任意进制之间转换数字
