PHP3中文文档（续5）

中文算术操作符这些工作和基本的学校里教的内容相似。Table 7-1. Arithmetic Operators（表7-1算术操作符）example name result$a + $b Addition Sum of $a and $b.?/FONT>$a - $b Subtraction Remainder of $b subtracted from $a.?/FONT>$a * $b Multiplication Product of $a and $b.?/FONT>$a / $b Division Dividend of $a and $b.?/FONT>$a % $b Modulus Remainder of $a divided by $b.其中，除法操作符“/”返回一个整数值（整数除法的结果）如果两个操作数是整数（或者是被转化成整数的字符串）的话。如果任意一个操作数是浮点数，那么将进行浮点运算。字符串操作符这个地方仅仅有一个真正的字符串操作符：串联符号“.”。$a = "Hello ";$b = $a . "World!";// now $b = "Hello World!"赋值操作符基本的赋值操作符就是“=”。您往往会倾向于认为它的含义就是“等于”。不要这样想，它真正的含义就是左侧的操作数获得右侧表达式的值。一个赋值表达式的意义在于值的指派。也就是说，“$a=3”的值是3。这就允许您做这样的事情：$a = ($b = 4) + 5;// $a is equal to 9 now, and $b has been set to 4.作为赋值操作符的一个补充，还有一个针对二进制数和字符传进行操作的组合操作符，该操作符允许您在赋值方采用被赋值表达式的值。例如：$a = 3;$a += 5; // sets $a to 8, as if we had said: $a = $a + 5;$b = "Hello ";$b .= "There!"; // sets $b to "Hello There!", just like $b = $b . "There!";位操作符位操作符允许您精细的操作数据的每一个位。Table 7-2. Bitwise Operators（表7-2位操作符）example     name                  result$a & $b    And    Bits that are set in both $a and $b are set.?/FONT>$a | $b    Or     Bits that are set in either $a or $b are set.?/FONT>~ $a?/FONT> Not   Bits that are set in $a are not set, and vice versa.逻辑操作符Table 7-3. Logical Operators（表7-3 逻辑操作符）example      name                    result?/FONT>$a and $b    And          True of both $a and $b are true.?/FONT>$a or $b     Or?/FONT>    True if either $a or $b is true.?/FONT>$a xor $b    Or?/FONT>    True if either $a or $b is true, but not both.?/FONT>! $a        Not?/FONT>    True if $a is not true.?/FONT>$a && $b    And?/FONT>    True of both $a and $b are true.?/FONT>$a || $b    Or?/FONT>     True if either $a or $b is true.比较操作符比较操作符，正如它的名字所示，允许您比较两个值。Table 7-4. Comparson Operators（表7-4 比较操作符）example          name       result?/FONT>$a == $b Equal?/FONT>  True if $a is equal to $b.?/FONT>$a != $b Not equal    True if $a is not equal to $b.?/FONT>$a    True if $a is strictly less than $b.?/FONT>$a > $b Greater than?/FONT>   True if $a is strictly greater than $b.?/FONT>$a   True if $a is less than or equal to $b.?/FONT>$a >= $b Greater than or equal to?/FONT>  True if $a is greater than or equal to $b.