of course this should be clear, but i think it has to be mentioned espacially:
AND is not the same like &&
for example:
<?php $a && $b || $c; ?>
is not the same like
<?php $a AND $b || $c; ?>
the first thing is
(a and b) or c
the second
a and (b or c)
'cause || has got a higher priority than and, but less than &&
of course, using always [ && and || ] or [ AND and OR ] would be okay, but than you should at least respect the following:
<?php $a = $b && $c; ?>
<?php $a = $b AND $c; ?>
the first code will set $a to the result of the comparison $b with $c, both have to be true, while the second code line will set $a like $b and THAN - after that - compare the success of this with the value of $c
maybe usefull for some tricky coding and helpfull to prevent bugs :D
greetz, Warhog
运算符
目录
运算符是可以通过给出的一或多个值（用编程行话来说，表达式）来产生另一个值（因而整个结构成为一个表达式）的东西。
运算符可按照其能接受几个值来分组。一元运算符只能接受一个值，例如
!（逻辑取反运算符）或
++（递增运算符）。
二元运算符可接受两个值，例如熟悉的算术运算符
+（加）和 -（减），大多数 PHP
运算符都是这种。最后是唯一的三元运算符 ? :，可接受三个值；通常就简单称之为“三元运算符”（尽管称之为条件运算符可能更合适）。
PHP 的运算符完整列表见下节运算符优先级。该节也解释了运算符优先级和结合方向，这控制着在表达式包含有若干个不同运算符时究竟怎样对其求值。
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User Contributed Notes 4 notes
Anonymous ¶
20 years ago
anisgazig at gmail dot com ¶
4 years ago
Operator are used to perform operation.
Operator are mainly divided by three groups.
1.Uniary Operators that takes one values
2.Binary Operators that takes two values
3.ternary operators that takes three values
Operator are mainly divided by three groups that are totally seventeen types.
1.Arithmetic Operator
+ = Addition
- = Subtraction
* = Multiplication
/ = Division
% = Modulo
** = Exponentiation
2.Assignment Operator
= "equal to
3.Array Operator
+ = Union
== = Equality
=== = Identity
!= = Inequality
<> = Inequality
!== = Non-identity
4.Bitwise Operator
& = and
^ = xor
| = not
<< = shift left
>> = shift right
5.Comparison Operator
== = equal
=== = identical
!= = not equal
!== = not identical
<> = not equal
< = less than
<= less than or equal
> = greater than
>= = greater than or equal
<=> = spaceship operator
6.Execution Operator
`` = backticks
7.Error Control Operator
@ = at sign
8.Incrementing/Decrementing Operator
++$a = PreIncrement
$a++ = PostIncrement
--$a = PreDecrement
$a-- = Postdecrement
9.Logical Operator
&& = And
|| = Or
! = Not
and = And
xor = Xor
or = Or
10.string Operator
. = concatenation operator
.= concatenating assignment operator
11.Type Operator
instanceof = instanceof
12.Ternary or Conditional operator
?: = Ternary operator
13.Null Coalescing Operator
??" = null coalescing
14.Clone new Operator
clone new = clone new
15.yield from Operator
yield from = yield from
16.yield Operator
yield = yield
17.print Operator
print = print
yasuo_ohgaki at hotmail dot com ¶
23 years ago
Other Language books' operator precedence section usually include "(" and ")" - with exception of a Perl book that I have. (In PHP "{" and "}" should also be considered also). However, PHP Manual is not listed "(" and ")" in precedence list. It looks like "(" and ")" has higher precedence as it should be.
Note: If you write following code, you would need "()" to get expected value.
<?php
$bar = true;
$str = "TEST". ($bar ? 'true' : 'false') ."TEST";
?>
Without "(" and ")" you will get only "true" in $str.
(PHP4.0.4pl1/Apache DSO/Linux, PHP4.0.5RC1/Apache DSO/W2K Server)
It's due to precedence, probably.
figroc at gmail dot com ¶
16 years ago
The variable symbol '$' should be considered as the highest-precedence operator, so that the variable variables such as $$a[0] won't confuse the parser. [http://www.php.net/manual/en/language.variables.variable.php]
