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    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

    up
    241
    Anonymous
    20 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
    up
    43
    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
    up
    14
    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 $str.
    (PHP4.0.4pl1/Apache DSO/Linux, PHP4.0.5RC1/Apache DSO/W2K Server)
    It's due to precedence, probably.
    up
    9
    figroc at gmail dot com
    16 years ago
    The variable symbol '$' 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]
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