PHP 8.3.14 Released!

    is_numeric

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

    is_numeric — 检测变量是否是数字或数字字符串

    说明

    is_numeric(mixed $value): bool

    检测变量是否是数字或数字字符串。

    参数

    value

    需要检测的变量。

    返回值

    如果 value 是数字或数字字符串， 返回 true，否则返回 false。

    更新日志

    版本 说明
    8.0.0 以空格结尾的数字字符串（"42 "）现在将返回 true。以前，会返回 false。

    示例

    示例 #1 is_numeric() 示例

    <?php
    $tests     = array(
    "42",
    1337,
    0x539,
    02471,
    0b10100111001,
    1337e0,
    "0x539",
    "02471",
    "0b10100111001",
    "1337e0",
    "not numeric",
    array(),
    9.1,
    null,
    '',
    );

    foreach (    $tests as $element) {
    if (    is_numeric($element)) {
    echo     var_export($element, true) . " is numeric", PHP_EOL;
    } else {
    echo     var_export($element, true) . " is NOT numeric", PHP_EOL;
    }
    }
    ?>

    以上示例会输出：

    '42' is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337.0 is numeric
'0x539' is NOT numeric
'02471' is numeric
'0b10100111001' is NOT numeric
'1337e0' is numeric
'not numeric' is NOT numeric
array (
) is NOT numeric
9.1 is numeric
NULL is NOT numeric
'' is NOT numeric

    示例 #2 带有空格的 is_numeric()

    <?php
    $tests     = [
    " 42",
    "42 ",
    "\u{A0}9001", // non-breaking space
    "9001\u{A0}", // non-breaking space
    ];
    foreach (    $tests as $element) {
    if (    is_numeric($element)) {
    echo     var_export($element, true) . " is numeric", PHP_EOL;
    } else {
    echo     var_export($element, true) . " is NOT numeric", PHP_EOL;
    }
    }
    ?>

    以上示例在 PHP 8 中的输出：

    ' 42' is numeric
'42 ' is numeric
' 9001' is NOT numeric
'9001 ' is NOT numeric

    以上示例在 PHP 7 中的输出：

    ' 42' is numeric
'42 ' is NOT numeric
' 9001' is NOT numeric
'9001 ' is NOT numeric

    参见

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    ＋添加备注

    用户贡献的备注 7 notes

    up
    94
    sobolanx at gmail dot com
    13 years ago
    Note that the function accepts extremely big numbers and correctly evaluates them.

    For example:

    <?php
    $v     = is_numeric ('58635272821786587286382824657568871098287278276543219876543') ? true : false;

    var_dump ($v);
    ?>

    The above script will output:

    bool(true)

    So this function is not intimidated by super-big numbers. I hope this helps someone.

    PS: Also note that if you write is_numeric (45thg), this will generate a parse error (since the parameter is not enclosed between apostrophes or double quotes). Keep this in mind when you use this function.
    up
    34
    tanguy_barsik at hotmail dot com
    7 years ago
    for strings, it return true only if float number has a dot

    is_numeric( '42.1' )//true
    is_numeric( '42,1' )//false
    up
    12
    moskalyuk at gmail dot com
    18 years ago
    is_numeric fails on the hex values greater than LONG_MAX, so having a large hex value parsed through is_numeric would result in FALSE being returned even though the value is a valid hex number
    up
    10
    ben at chico dot com
    10 years ago
    Apparently NAN (Not A Number) is a number for the sake of is_numeric().

    <?php
    echo "is ";
    if (!    is_numeric(NAN))
    echo     "not ";
    echo     "a number";
    ?>

    Outputs "is a number". So something that is NOT a number (by defintion) is a number...
    up
    6
    kouber at saparev dot com
    20 years ago
    Note that this function is not appropriate to check if "is_numeric" for very long strings. In fact, everything passed to this function is converted to long and then to a double. Anything greater than approximately 1.8e308 is too large for a double, so it becomes infinity, i.e. FALSE. What that means is that, for each string with more than 308 characters, is_numeric() will return FALSE, even if all chars are digits.

    However, this behaviour is platform-specific.

    http://www.php.net/manual/en/language.types.float.php

    In such a case, it is suitable to use regular expressions:

    function is_numeric_big($s=0) {
    return preg_match('/^-?\d+$/', $s);
    }
    up
    3
    Magnus Deininger, dma05 at web dot de
    15 years ago
    regarding the global vs. american numeral notations, it should be noted that at least in japanese, numbers aren't grouped with an extra symbol every three digits, but rather every four digits (for example 1,0000 instead of 10.000). also nadim's regexen are slightly suboptimal at one point having an unescaped '.' operator, and the whole thing could easily be combined into a single regex (speed and all).

    adjustments:

    <?php
    $eng_or_world     = preg_match
    ('/^[+-]?'. // start marker and sign prefix
    '(((([0-9]+)|([0-9]{1,4}(,[0-9]{3,4})+)))?(\\.[0-9])?([0-9]*)|'. // american
    '((([0-9]+)|([0-9]{1,4}(\\.[0-9]{3,4})+)))?(,[0-9])?([0-9]*))'. // world
    '(e[0-9]+)?'. // exponent
    '$/', // end marker
    $str) == 1;
    ?>

    i'm sure this still isn't optimal, but it should also cover japanese-style numerals and it fixed a couple of other issues with the other regexen. it also allows for an exponent suffix, the pre-decimal digits are optional and it enforces using either grouped or ungrouped integer parts. should be easier to trim to your liking too.
    up
    0
    Katrina Kizenbach
    1 year ago
    Note that is_numeric() will evaluate to false for number strings using decimal commas.

    is_numeric('0.11');
    Output: true

    is_numeric('0,11');
    Output: false
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