(PHP 4, PHP 5, PHP 7, PHP 8)
bindec — 二進(jìn)制轉換為十進(jìn)制
$binary_string): number
返回
binary_string 參數所表示的二進(jìn)制數的十進(jìn)制等價(jià)值。
bindec() 將一個(gè)二進(jìn)制數轉換成 integer，或者出于大小的需要，轉換為 float 類(lèi)型。
bindec() 將所有的
binary_string 值解釋為無(wú)符號整數。這是由于
bindec() 函數將其最高有效位視為數量級而非符號位。
binary_string要轉換的二進(jìn)制字符串
參數必須為字符串。使用其他數據類(lèi)型會(huì )導致不可預知的結果。
binary_string 的十進(jìn)制數值
| 版本 | 說(shuō)明 |
|---|---|
| 4.1.0 | 本函數如今可以轉換超過(guò)程序運行平臺中 integer 類(lèi)型最大值的數，此時(shí)其值會(huì )返回為 float 類(lèi)型。 |
示例 #1 bindec() 例子
<?php
echo bindec('110011') . "\n";
echo bindec('000110011') . "\n";
echo bindec('111');
?>
以上例程會(huì )輸出：
51 51 7
示例 #2 bindec() 將輸入解讀為無(wú)符號整數
<?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 位機器上的輸出:
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 位機器上的輸出:
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