Arithmetic operators
1. Arithmetic operators: +, -, *, /, %.
2. Increment/decrement operators: such as $a++,$a--,++$a,--$a.
For example:
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echo '$a='.$a."||".'$c='.$c.'
$c=++$a; //increment first, then assign value. $a=$a+1,$c=$a $d=--$b; //decrement first, then assign value. $b=$a-1, $d=$b
echo '$a='.$a."||".'$c='.$c.' '; //$b=4,$d=4
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Ternary operator
(expr1) ? (expr2) : (expr3); Explanation: If condition "expr1" is true, execute statement "expr2", otherwise execute "expr3".
The following statements are syntactically correct, they omit the second or third "element" in small dequotation marks:代码如下 | 复制代码 |
$a=10;$b=7; 改变一下 $a=10;$b=7; |
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$a>$b ? print "Yes" : ""; $a>$b ? '': print 'No'; |
The code is as follows | Copy code |
$str = $_GET['abc'] ? 'wangjinbo' : 'wjb'; |
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$a=10;$b=7; if($a++>8 || $b++>7){ //$a++>8 is true, $b++>7 will not be executed echo 'OK!'; } echo 'a='.$a.'b='.$b; // Output OK, a=11,b=7 Change it up $a=10;$b=7; if($a++>10 && $b++>7){ //$a++>8 is false, $b++>7 will not be executed echo 'OK!'; } echo 'a='.$a.'b='.$b; // a=11,b=7 |
Details: and && both represent logical AND, what is their difference?
Mainly reflected in priority
Priority of and
代码如下 | 复制代码 |
and
or
如: $a=false || true; //&& > = > and ;先比较false || true,再赋值 $b=false or true; //|| > = > or ;先赋值$b=false,再比较,所以结果是false var_dump($a,$b); //bool(true) bool(false) |
Bitwise operators
Displacement is a mathematical operation in PHP. Bits moved out in any direction are discarded. When shifting left, the right side is padded with zeros, and the sign bit is moved away, meaning that the sign is not preserved. When shifting right, the left side is padded with sign bits, which means the sign is preserved.
Use parentheses to ensure desired precedence. For example, $a & $b == true performs comparison first and then performs bitwise AND; while ($a & $b) == true performs bitwise AND first and then performs comparison.
Pay attention to data type conversion. If both left and right arguments are strings, the bitwise operators operate on the ASCII values of the characters.
PHP’s ini setting error_reporting uses bitwise values,
Real-life examples of turning off a bit are provided. To show except prompt level
For all errors except php.ini, use this:
E_ALL & ~E_NOTICE
The specific operation method is to first obtain the value of E_ALL:
00000000000000000111011111111111
Then get the value of E_NOTICE:
00000000000000000000000000001000
Then negate it via ~:
11111111111111111111111111110111
Finally, use bitwise AND (&) to get the bits that are set (to 1) in both values:
00000000000000000111011111110111
Another method is to use bitwise XOR (^) to get only the values in
The bits set in one of the values:
E_ALL ^ E_NOTICE
error_reporting can also be used to demonstrate how to set the bit. Show only errors and recoverables
The wrong way is:
E_ERROR | E_RECOVERABLE_ERROR
That is to say, E_ERROR
00000000000000000000000000000001
and E_RECOVERABLE_ERROR
00000000000000000001000000000000
Use the bitwise OR (|) operator to get the result of a bit being set in any value:
00000000000000000001000000000001
Example #1 AND, OR and XOR bitwise operators for integers
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Comparison operators
If comparing a number to a string or comparing strings involving numeric content, the string is converted to a numeric value and the comparison is performed as a numeric value. This rule also applies to switch statements. When comparing with === or !==, no type conversion is performed because both types and values are compared.
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var_dump("1" == "01"); // 1 == 1 -> true var_dump("10" == "1e1"); // 10 == 10 -> true var_dump(100 == "1e2"); // 100 == 100 -> true switch ("a") { case 0: echo "0"; Break; case "a": // never reached because "a" is already matched with 0 echo "a"; Break; } ?>
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For multiple types, comparison operators compare according to the following table (in order).

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。

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。

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。

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。

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。

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。


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