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

ctype_xdigit Check for character(s) representing a hexadecimal digit


bool ctype_xdigit ( string $text )

Checks if all of the characters in the provided string, text, are hexadecimal 'digits'.



The tested string.


Returns TRUE if every character in text is a hexadecimal 'digit', that is a decimal digit or a character from [A-Fa-f] , FALSE otherwise.


Example #1 A ctype_xdigit() example

= array('AB10BC99''AR1012''ab12bc99');
foreach (
$strings as $testcase) {
    if (
ctype_xdigit($testcase)) {
"The string $testcase consists of all hexadecimal digits.\n";
    } else {
"The string $testcase does not consist of all hexadecimal digits.\n";

위 예제의 출력:

The string AB10BC99 consists of all hexadecimal digits.
The string AR1012 does not consist of all hexadecimal digits.
The string ab12bc99 consists of all hexadecimal digits.



-128이상 255이하의 integer를 지정할 경우, 한 문자의 ASCII 값으로 해석합니다. (음수는 256이 더해져 확장 ASCII 영역의 문자가 됩니다) 그 외의 정수는 그 정수를 표현하는 10진 문자열로 해석합니다.


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User Contributed Notes 1 note

tom at hgmail dot com
16 years ago
This function shows its usefulness on a web site where a user is asked to entered a hexidecimal color code for a color. To prevent breaking W3C standard and having them enter in "neon-green" or the wrong type of code like 355511235.

In conjunction with strlen()  you could create a function like this:

function check_valid_colorhex($colorCode) {
    // If user accidentally passed along the # sign, strip it off
    $colorCode = ltrim($colorCode, '#');

    if (
          ctype_xdigit($colorCode) &&
          (strlen($colorCode) == 6 || strlen($colorCode) == 3))
               return true;

    else return false;
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