ctype_digit()

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

做纯数字检测

说明

ctype_digit(string $text): bool

检查提供的string和$text里面的字符是不是都是数字。

参数

$text: 需要被测试的字符串。

返回值

如果$text字符串是一个十进制数字，就返回TRUE；反之就返回FALSE。

更新日志

版本	说明
5.1.0	在 PHP 5.1.0 之前，当`$text`是一个空字符串的时候，该函数将返回`TRUE`。

范例

一个ctype_digit()例子

<?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";
    }
}
?>

以上例程会输出：

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.

一个通过ctype_digit()来比对字符和整数的例子。

<?php
$numeric_string = '42';
$integer        = 42;
ctype_digit($numeric_string);  // true
ctype_digit($integer);         // false (ASCII 42 is the * character)
is_numeric($numeric_string);   // true
is_numeric($integer);          // true
?>

注释

Note:
这个函数的参数要求是一个string这一点是非常有用的，因此当你传入一个integer的参数也许不能得到期望的结果。然后，同样需要注意HTML表单将会返回数字字符串而不是一个整型。看下手册的types章节。

Note:
如果给出一个-128 到 255 之间(含)的整数,将会被解释为该值对应的ASCII字符(负值将加上 256 以支持扩展ASCII字符).其它整数将会被解释为该值对应的十进制字符串.

参见

ctype_alnum()做字母和数字字符检测
ctype_xdigit()检测字符串是否只包含十六进制字符
is_numeric()检测变量是否为数字或数字字符串
is_int()检测变量是否是整数
is_string()检测变量是否是字符串

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;
    }
  }
?>

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

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

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.

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)

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

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.

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.

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.

If you need to check for integers instead of just digits you can supply your own function such as this:
<?php
function ctype_int($text)
{
  return preg_match('/^-?[0-9]+$/', (string)$text) ? true : false;
}
?>

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

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);
}

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.