PHP Velho Oeste 2024

演算子

目次

演算子とは、ひとつ以上の値 (あるいはプログラミング用語における「式」) から別の値 (制御構造が式になるように) を生み出すものです。

演算子は、受け取る値の数によって分類することができます。単項演算子はひとつの値だけを受け取るもので、 ! ( 論理否定演算子) や ++ ( 加算子) などです。二項演算子はふたつの値を受け取ります。おなじみの 算術演算子 である + (加算) や - (減算) など PHP の演算子の大半はこの分類に含まれます。最後は三つの値を受け取る 三項演算子 で、これは ? : だけしかありません。この演算子はしばしば、単に "三項演算子" と呼ばれます (しかし、より適切な呼び方としては 条件演算子と呼ぶほうがよいでしょう)。

PHP の演算子の完全な一覧は、 演算子の優先順位 の欄にあります。この節では演算子の優先順位と結合性について説明します。 複数の演算子を組み合わせたときにどう評価されるのかは、優先順位と結合性で決まります。

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User Contributed Notes 4 notes

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252
Anonymous
19 years ago
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
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52
anisgazig at gmail dot com
3 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
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24
yasuo_ohgaki at hotmail dot com
22 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 $str.
(PHP4.0.4pl1/Apache DSO/Linux, PHP4.0.5RC1/Apache DSO/W2K Server)
It's due to precedence, probably.
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4
figroc at gmail dot com
15 years ago
The variable symbol '$' 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]
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