is_numeric

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

is_numeric — 変数が数字または数値形式の文字列であるかを調べる

説明

is_numeric(mixed $value): bool

指定した変数が数値または数値形式の文字列であるかどうかを調べます。

パラメータ

value: 評価する変数。

戻り値

value が数値または数値形式の文字列である場合に true、それ以外の場合に false を返します。

変更履歴

バージョン	説明
8.0.0	空白文字で終わる数値形式の文字列 (`"42 "`) に対して、この関数は `true` を返すようになりました。これより前のバージョンでは、`false` を返していました。

例

例1 is_numeric() の例

<?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;
    }
}
?>

上の例の出力は以下となります。

'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

例2 空白文字と is_numeric() 関数

<?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;
    }
}
?>

上の例の PHP 8 での出力は、このようになります。:

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

上の例の PHP 7 での出力は、このようになります。

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

参考

数値形式の文字列
ctype_digit() - 数字かどうかを調べる
is_bool() - 変数が boolean であるかを調べる
is_null() - 変数が null かどうか調べる
is_float() - 変数の型が float かどうか調べる
is_int() - 変数が整数型かどうかを検査する
is_string() - 変数の型が文字列かどうかを調べる
is_object() - 変数がオブジェクトかどうかを検査する
is_array() - 変数が配列かどうかを検査する
filter_var() - 指定したフィルタでデータをフィルタリングする

Found A Problem?

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 7 notes

down

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.

down

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

down

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

down

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...

down

kouber at saparev dot com ¶

21 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);
}

down

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.

down

Katrina Kizenbach ¶

2 years 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

＋add a note