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    is_float

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

    is_float — 查找变量的类型是否是浮点型

    说明

    is_float(mixed $value): bool

    查找指定变量的类型是否是浮点型。

    注意:

    测试变量是数字还是数字字符串（如表单输入，始终是字符串），必须使用 is_numeric()。

    参数

    value

    要求值的变量。

    返回值

    如果 value 是 float，返回 true，否则返回 false。

    示例

    示例 #1 is_float() 示例

    <?php

    var_dump    (is_float(27.25));
    var_dump(is_float('abc'));
    var_dump(is_float(23));
    var_dump(is_float(23.5));
    var_dump(is_float(1e7)); // 科学计数
    var_dump(is_float(true));
    ?>

    以上示例会输出：

    bool(true)
bool(false)
bool(false)
bool(true)
bool(true)
bool(false)

    参见

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    User Contributed Notes 6 notes

    up
    21
    nonzer0value
    9 years ago
    Coercing the value to float and back to string was a neat trick. You can also just add a literal 0 to whatever you're checking.

    <?php
    function isfloat($value) {
          // PHP automagically tries to coerce $value to a number
          return is_float($value + 0);
    }
    ?>

    Seems to work ok:

    <?php
    isfloat    ("5.0" + 0);  // true
    isfloat("5.0");  // false
    isfloat(5 + 0);  // false
    isfloat(5.0 + 0);  // false
    isfloat('a' + 0);  // false
    ?>

    YMMV
    up
    21
    Boylett
    16 years ago
    If you want to test whether a string is containing a float, rather than if a variable is a float, you can use this simple little function:

    function isfloat($f) return ($f == (string)(float)$f);
    up
    4
    Anonymous
    3 years ago
    is_float() returns true for NAN, INF and -INF. You may want to test is_float($value) && is_finite($value), or alternatively filter_var($value, FILTER_VALIDATE_FLOAT) !== false.
    up
    7
    kshegunov at gmail dot com
    16 years ago
    As celelibi at gmail dot com stated, is_float checks ONLY the type of the variable not the data it holds!

    If you want to check if string represent a floating point value use the following regular expression and not is_float(),
    or poorly written custom functions.

    /^[+-]?(([0-9]+)|([0-9]*\.[0-9]+|[0-9]+\.[0-9]*)|
    (([0-9]+|([0-9]*\.[0-9]+|[0-9]+\.[0-9]*))[eE][+-]?[0-9]+))$/
    up
    6
    Erutan409 at Hotmail dot com
    9 years ago
    Boylett's solution is elegant (http://php.net/manual/en/function.is-float.php#85848), but won't work for long float's or variables that are not explicitly type of 'string' or for long floats that are encased in quotes, making it a string that will be truncated/rounded when cast to a float.  So, further logic must be completed to test for the case.  Take the following example:

    <?php

    if (!function_exists("test_float")) {

        function     test_float($test) {

            if (!    is_scalar($test)) {return false;}

                $type = gettype($test);

            if (    $type === "float") {
                return     true;
            } else {
                return     preg_match("/^\\d+\\.\\d+$/", $test) === 1;
            }

        }

    }

    $test = "3.14159265358979323846264338g32795";

    var_dump($test);
    var_dump((float)$test);
    var_dump($test == (string)(float)$test);
    var_dump(test_float($test));

    ?>

    Will produce (32-bit):

    string(34) "3.14159265358979323846264338g32795"
    float(3.1415926535898)
    bool(false)
    bool(false)

    So far, so good, right?  Yeah, but it's misleading, because the string is so long, that when it's converted to a float, it won't be equivalent to the comparison of the value being cast back into a string .  So the aforementioned short function works.  Look at this next example:

    <?php

    $test     = 3.1415926535897932384626433832795;

    var_dump($test);
    var_dump((float)$test);
    var_dump($test == (string)(float)$test);
    var_dump(test_float($test));

    ?>

    Will produce (32-bit):

    float(3.1415926535898)
    float(3.1415926535898)
    bool(false)
    bool(true)

    Why is it not working now, but the value is truly a float?  Same reasoning as mentioned before.  The float is so long that it's truncated/rounded and doesn't match the comparison being done with the short-hand function.

    So, as you can see, more logic should be applied to the variable you're testing.
    up
    6
    KIVagant at gmail dot com
    12 years ago
    Yet another regular expression for float in real life:

    <?php
    function isTrueFloat($val)
    {
            $pattern = '/^[-+]?(((\\\\d+)\\\\.?(\\\\d+)?)|\\\\.\\\\d+)([eE]?[+-]?\\\\d+)?$/';

        return (!    is_bool($val) && (is_float($val) || preg_match($pattern, trim($val))));
    }
    ?>

    // Matches:
    1, -1, 1.0, -1.0, '1', '-1', '1.0', '-1.0', '2.1', '0', 0, ' 0 ', ' 0.1 ', ' -0.0 ', -0.0, 3., '-3.', '.27', .27, '-0', '+4', '1e2', '+1353.0316547', '13213.032468e-13465', '-8E+3', '-1354.98879e+37436'

    // Non-matches:
    false, true, '', '-', '.a', '-1.a', '.a', '.', '-.', '1+', '1.3+', 'a1', 'e.e', '-e-4', 'e2', '8e', '3,25'
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