Attributed to Solomon W. Golomb; a method for swapping the values of two integer variables without using an intermediate variable (you can tell this dates from the Elder Days, when variables were expensive!). Thanks to PHP's syntax it's also a one-liner.
$a^=$b^=$a^=$b;
Okay, here's how it goes (yeah, like I need to make content-free posts just for the sake of an increment...).
First, simplify the line; noting that ^= is right-associative, which means that in that line the rightmost operator is evaluated first, that the assignment operators also return the value that they assign to their lvalue, and that foo^=bar is shorthand for foo=foo^bar:
Code:
<br />$a^=$b^=$a^=$b;<br />$a^=($b^=($a^=$b));<br />$a=$a^b;<br />$a^=($b^=$a);<br />$a=$a^$b;<br />$b=$b^$a;<br />$a=$a^$b;<br />
Recall what ^ does. Takes each pair of corresponding bits from its arguments (the internal binary representation of its arguments, that is), and xors them together to produce the corresponding bit of the result ("corresponding" means that the first bits of both arguments produce the first bit of the result, the second bits of both arguments produce the second bit of the result, and so on. This is why, as BuzzLY noted, it's important that both variables are the same size - demons probably start flying out of your nose if one of them runs out of bits to xor before the other. So to figure out what ^ does to a pair of variables, we only need to recap what it does to single bits

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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