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    floor

    (PHP 4, PHP 5, PHP 7, PHP 8)

    floor — 端数の切り捨て

    説明

    floor(int|float $num): float

    必要に応じて num を丸めることにより、 num をこえない最大の整数の値を (float 型で) 返します。

    パラメータ

    num

    丸める数値。

    戻り値

    num をこえない最大の整数の値を返します。 floor() の戻り値は float 型のままとなります。

    変更履歴

    バージョン 説明
    8.0.0 num は、 数値への変換をサポートした内部オブジェクトを受け入れなくなりました。

    例

    例1 floor() の例

    <?php
    echo floor(4.3); // 4
    echo floor(9.999); // 9
    echo floor(-3.14); // -4
    ?>

    参考

    • ceil() - 端数の切り上げ
    • round() - 浮動小数点数を丸める

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    User Contributed Notes 3 notes

    up
    16
    Antonio
    5 years ago
    <?php
    echo (2.3 * 100) . ' - ' . round(2.3 * 100, 0) . ' - ' . floor(2.3 * 100);
    ?>.

    Result:
    230 - 230 - 229

    Be careful!
    up
    10
    jay at w3prodigy dot com
    16 years ago
    Note:

    <?php
    $int     = 0.99999999999999999;
    echo     floor($int); // returns 1
    ?>

    and

    <?php
    $int     = 0.9999999999999999;
    echo     floor($int); // returns 0
    ?>
    up
    8
    jolyon at mways dot co dot uk
    20 years ago
    Beware of FLOAT weirdness!

    Floats have a mind of their own, and what may look like an integer stored in a float isn't.

    Here's a baffling example of how floor can be tripped up by this:

    <?php
    $price     = 79.99;

    print     $price."\r\n"; // correct result, 79.99 shown

    $price = $price * 100;

    print     $price."\r\n"; // correct result, 7999 shown

    print floor($price); // 7998 shown! what's going on?
    ?>

    The thing to remember here is that the way a float stores a value makes it very easy for these kind of things to happen. When the 79.99 was multiplied by 100, the actual value stored in the float was probably something like 7998.9999999999999999999999999999999999, PHP would print out 7999 when the value is displayed but floor would therefore round this down to 7998.

    THe moral of this story - never use float for anything that needs to be accurate! If you're doing prices for products or a shopping cart, then always use an integer and store prices as a number of pence, you'll thank me for this later :)
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