PHP 5.6.0RC3 is available

ctype_digit

(PHP 4 >= 4.0.4, PHP 5)

ctype_digitCheck for numeric character(s)

Description

bool ctype_digit ( string $text )

Checks if all of the characters in the provided string, text, are numerical.

Parameters

text

The tested string.

Return Values

Returns TRUE if every character in the string text is a decimal digit, FALSE otherwise.

Changelog

Version Description
5.1.0 Before PHP 5.1.0, this function returned TRUE when text was an empty string.

Examples

Example #1 A ctype_digit() example

<?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";
    }
}
?>

The above example will output:

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.

Example #2 A ctype_digit() example comparing strings with integers

<?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
?>

Notes

Note:

This function expects a string to be useful, so for example passing in an integer may not return the expected result. However, also note that HTML forms will result in numeric strings and not integers. See also the types section of the manual.

Note:

If an integer between -128 and 255 inclusive is provided, it is interpreted as the ASCII value of a single character (negative values have 256 added in order to allow characters in the Extended ASCII range). Any other integer is interpreted as a string containing the decimal digits of the integer.

See Also

  • ctype_alnum() - Check for alphanumeric character(s)
  • ctype_xdigit() - Check for character(s) representing a hexadecimal digit
  • is_numeric() - Finds whether a variable is a number or a numeric string
  • is_int() - Find whether the type of a variable is integer
  • is_string() - Find whether the type of a variable is string

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User Contributed Notes 10 notes

up
16
info at directwebsolutions dot nl
2 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;
        }
    }
?>
up
7
rlerne at gmail dot com
1 year 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.
up
6
John Saman
4 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.
up
6
strrev xc tod noxeh ta ellij
4 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)
up
7
a_p_leeming at hotmail dot com
5 years ago
Also note that

<?php ctype_digit("-1");   //false ?>
up
6
Peter de Pijd
5 years ago
Note that an empty string is also false:
ctype_digit("") // false
up
1
raul dot 3k at gmail dot com
5 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
up
0
Skippy
2 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;
}
?>
up
0
mdsky at web dot de
4 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.
up
-12
Anonymous
5 years ago
Indeed, ctype_digit only functions correctly on strings. Cast your vars to string before you test them. Also, be wary and only use ctype_digit if you're sure your var contains either a string or int, as boolean true for ex will convert to int 1.

To be truly safe, you need to check the type of the var first. Here's a wrapper function that improves upon ctype_digit's broken implementation:

<?php

// replacement for ctype_digit, to properly
// handle (via return value false) nulls,
// booleans, objects, resources, etc.
function ctype_digit2 ($str) {
    return (
is_string($str) || is_int($str) || is_float($str)) &&
       
ctype_digit((string)$str);
}

?>

If, like me, you're not willing to take a chance on ctype_digit having other problems, use this version:

<?php

// replacement for ctype_digit, to properly
// handle (via return value false) nulls,
// booleans, objects, resources, etc.
function ctype_digit2 ($str) {
    return (
is_string($str) || is_int($str) || is_float($str)) &&
       
preg_match('/^\d+\z/', $str);
}

?>
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