PHP/Data Type/ctype digit
Validating a number with ctype_digit()
<source lang="html4strict">
<?php if (! ctype_digit($_POST["age"])) {
print "Your age must be a number bigger than or equal to zero.";
} ?>
</source>
<source lang="html4strict">
<?php if (! ctype_digit($_POST["age"])) {
print "Your age must be a number bigger than or equal to zero.";
} ?>
</source>