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;
}
}
?>
ctype_digit
(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
ctype_digit — 检测数字字符
参数
返回值
如果 text 中每个字符都是十进制数字，那么就返回
true，否则返回 false。当使用空字符串调用时，结果始终为 false。
示例
示例 #1 ctype_digit() 示例
<?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";
}
}
?>以上示例会输出：
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.
示例 #2 ctype_digit() 示例，比对字符和整数
<?php
$numeric_string = '42';
$integer = 42;
ctype_digit($numeric_string); // true
ctype_digit($integer); // false（ASCII 42 是 * 字符）
is_numeric($numeric_string); // true
is_numeric($integer); // true
?>参见
- ctype_alnum() - 检测字母数字式字符
- ctype_xdigit() - 检测字符是否只包含十六进制字符
- is_numeric() - 检测变量是否为数字或数字字符串
- is_int() - 检测变量是否是整数
- is_string() - 查找变量的类型是否是字符串
- IntlChar::isdigit() - Check if code point is a digit character
add a note
User Contributed Notes 14 notes
info at directwebsolutions dot nl ¶
12 years ago
smicheal2 at gmail dot com ¶
9 years ago
Please note that ctype_digit() will say true for strings such as '00001', which are not technically valid representations of integers, while saying false to strings such as '-1', which are. It's basically a faster version of the regex /^\d+$/. 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.
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
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) $val);
?>
Which will also return true, as it should.
strrev xc tod noxeh ta ellij ¶
15 years ago
ctype_digit() will treat all passed integers below 256 as character-codes. It returns true for 48 through 57 (ASCII '0'-'9') and false for the rest.
ctype_digit(5) -> false
ctype_digit(48) -> true
ctype_digit(255) -> false
ctype_digit(256) -> true
(Note: the PHP type must be an int; if you pass strings it works as expected)
mdsky at web dot de ¶
14 years ago
is_numeric gives true by f. ex. 1e3 or 0xf5 too. So it's not the same as ctype_digit, which just gives true when only values from 0 to 9 are entered.
John Saman ¶
14 years ago
Using is_numeric function is quite faster than ctype_digit.
is_numeric took 0.237 Seconds for one million runs. while ctype_digit took 0.470 Seconds.
Skippy ¶
13 years ago
If you need to check for integers instead of just digits you can supply your own function such as this:
<?php
function ctype_int($text)
{
return preg_match('/^-?[0-9]+$/', (string)$text) ? true : false;
}
?>
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.
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
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) $digit);
}
divinity76 at gmail dot com ¶
3 years ago
an alternative if you want to check if it's a valid integer:
<?php
if(false!==filter_var($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
}
?>
