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

ctype_xdigit Check for character(s) representing a hexadecimal digit


ctype_xdigit(mixed $text): bool

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



The tested string.


If an int 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.


As of PHP 8.1.0, passing a non-string argument is deprecated. In the future, the argument will be interpreted as a string instead of an ASCII codepoint. Depending on the intended behavior, the argument should either be cast to string or an explicit call to chr() should be made.

Return Values

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. When called with an empty string the result will always be false.


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";

The above example will output:

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.

See Also

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User Contributed Notes 2 notes

tom at hgmail dot com
18 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;
1 year ago
this can be used with great results if you wanna check for something like

"Tobias2" whether there is a number at the end of the string. (F.e. courselist with coursenames etc.)

Just substring the last char and put it in the function.
We should be glad about every possibility to cut out these damn regexes from our code. NEVER USE REGEX
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