ctype_digit

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

ctype_digit — 数字かどうかを調べる

説明

ctype_digit(mixed $text): bool

与えられた文字列 text のすべての文字が数字であるかどうかを調べます。

パラメータ

text

調べる文字列。

注意:
-128 から 255 までの int を渡すと、ひとつの文字の ASCII 値とみなします (負の値には 256 を足して、拡張 ASCII の範囲に収まるようにします)。それ以外の整数値は、10 進数を含む文字列とみなします。

警告

PHP 8.1.0 以降は、ctype関数に文字列でない引数を渡すことは、推奨されなくなりました。将来のバージョンでは、引数は ASCII コードポイントではなく、文字列として解釈されるようになります。ユーザが意図する振る舞いによっては、引数を文字列にキャストするか、 chr() を明示的にコールすべきです。

戻り値

string text のすべての文字が 10 進数字だった場合に true、そうでない場合に false を返します。空文字列を渡して呼び出した場合、結果は常に false になります。

例

例1 ctype_digit() の例

<?php
$strings = array('1820.20', '10002', 'wsl!12');
foreach ($strings as $testcase) {
    if (ctype_digit($testcase)) {
        echo "The string $testcase consists of all digits.\n";
    } else {
        echo "The string $testcase does not consist of all digits.\n";
    }
}
?>

上の例の出力は以下となります。

The string 1820.20 does not consist of all digits.
The string 10002 consists of all digits.
The string wsl!12 does not consist of all digits.

例2 ctype_digit() で文字列と整数値を比較する例

<?php

$numeric_string = '42';
$integer        = 42;

ctype_digit($numeric_string);  // true
ctype_digit($integer);         // false (ASCII 42 は * です)

is_numeric($numeric_string);   // true
is_numeric($integer);          // true
?>

参考

ctype_alnum() - 英数字かどうかを調べる
ctype_xdigit() - 16 進数を表す文字かどうかを調べる
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
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
IntlChar::isdigit() - コードポイントが、数字であるかを調べる

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User Contributed Notes 13 notes

down

info at directwebsolutions dot nl ¶

12 years ago

All basic PHP functions which i tried returned unexpected results. I would just like to check whether some variable only contains numbers. For example: when i spread my script to the public i cannot require users to only use numbers as string or as integer. For those situation i wrote my own function which handles all inconveniences of other functions and which is not depending on regular expressions. Some people strongly believe that regular functions slow down your script.

The reason to write this function:
1. is_numeric() accepts values like: +0123.45e6 (but you would expect it would not)
2. is_int() does not accept HTML form fields (like: 123) because they are treated as strings (like: "123").
3. ctype_digit() excepts all numbers to be strings (like: "123") and does not validate real integers (like: 123).
4. Probably some functions would parse a boolean (like: true or false) as 0 or 1 and validate it in that manner.

My function only accepts numbers regardless whether they are in string or in integer format.
<?php
    /**
     * Check input for existing only of digits (numbers)
     * @author Tim Boormans <info@directwebsolutions.nl>
     * @param $digit
     * @return bool
     */
    function is_digit($digit) {
        if(is_int($digit)) {
            return true;
        } elseif(is_string($digit)) {
            return ctype_digit($digit);
        } else {
            // booleans, floats and others
            return false;
        }
    }
?>

down

smicheal2 at gmail dot com ¶

9 years ago

Please note that ctype_digit() will say true for strings such as '00001', which are not technically valid representations of integers, while saying false to strings such as '-1', which are. It's basically a faster version of the regex /^\d+$/. As the name says, it answers the question "does this string contain only digits" literally. It does not answer "is this a valid representation of an integer". If that's what you want, use is_int(filter_var($val, FILTER_VALIDATE_INT)) instead.

down

Peter de Pijd ¶

15 years ago

Note that an empty string is also false:
ctype_digit("") // false

down

error17191 at gmail dot com ¶

9 years ago

I just wanted to clarify a flaw in the function is_digit() suggested by "info at directwebsolutions dot nl " .. 
It returns true in case of negative integers and false in case of strings that contain negative integers .
 example:
is_digit(-10); // returns ture
is_digit('-10'); // returns false

down

rlerne at gmail dot com ¶

11 years ago

Interesting to note that you must pass a STRING to this function, other values won't be typecasted (I figured it would even though above explicitly says string $text).

I.E.

<?PHP
$val = 42; //Answer to life
$x = ctype_digit($val);
?>

Will return false, even though, when typecasted to string, it would be true.

<?PHP
$val = '42';
$x = ctype_digit($val);
?>

Returns True.

Could do this too:

<?PHP
$val = 42;
$x = ctype_digit((string) $val);
?>

Which will also return true, as it should.

down

strrev xc tod noxeh ta ellij ¶

15 years ago

ctype_digit() will treat all passed integers below 256 as character-codes. It returns true for 48 through 57 (ASCII '0'-'9') and false for the rest.

ctype_digit(5) -> false
ctype_digit(48) -> true
ctype_digit(255) -> false
ctype_digit(256) -> true

(Note: the PHP type must be an int; if you pass strings it works as expected)

down

a_p_leeming at hotmail dot com ¶

15 years ago

Also note that



<?php ctype_digit("-1");   //false ?>

down

mdsky at web dot de ¶

14 years ago

is_numeric gives true by f. ex. 1e3 or 0xf5 too. So it's not the same as ctype_digit, which just gives true when only values from 0 to 9 are entered.

down

John Saman ¶

14 years ago

Using is_numeric function is quite faster than ctype_digit.

is_numeric took 0.237 Seconds for one million runs. while ctype_digit took 0.470 Seconds.

down

-3

zorrosNOSPAMwordsman at NOSPAM dot gmail dot com ¶

8 years ago

If you want to verify whether or not a variable contains only digits, you can type cast it to a string and back to int and see if the result is identical. Like so:

<?php

// (bool) TRUE if only digits, FALSE otherwise
$isOnlyDigits = (string) (int) $input === (string) $input;

?>

I haven't benchmarked it, but I'm guessing it's significantly faster then regular expressions.

down

-5

raul dot 3k at gmail dot com ¶

15 years ago

The ctype_digit can be used in a simple form to validate a field:
<?php
$field = $_POST["field"];
if(!ctype_digit($field)){
  echo "It's not a digit";
}
?>

Note:
Digits is 0-9

down

-3

brcontainer at yahoo dot com dot br ¶

6 years ago

ctype_digit don't support negative value in string:

<?php
var_dump( ctype_digit('-10') ); //return bool(false)
?>

Improved (and simplified) Tim Boormans code:

<?php
/**
 * Check input for existing only of digits (numbers)
 * @author Guilherme Nascimento <brcontainer@yahoo.com.br>
 * @param $digit
 * @return bool
 */
function is_digit($digit)
{
    return preg_match('#^-?\d+$#', $digit) && is_int((int) $digit);
}

down

-5

divinity76 at gmail dot com ¶

3 years ago

an alternative if you want to check if it's a valid integer: 

<?php
if(false!==filter_var($v, FILTER_VALIDATE_INT)){
    // it's a valid int!
    $v=(int)$v;
}else{
    // it's not a valid int
}
?>

or if you want to check that it's a positive integer (>= 0): 
<?php
if(false!==filter_var($v, FILTER_VALIDATE_INT, ["options"=>["min_range"=>0]])){
    // it's a valid positive integer!
    $v = (int)$v;
}else{
    // it's not a valid positive integer
}

?>

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