IntroductionThe functions provided by this extension check whether a character or string falls into a certain character class according to the current locale (see also setlocale). When called with an integer argument these functions behave exactly like their C counterparts from ctype.h. It means that if an integer smaller than 256 is passed, it will use the ASCII value of it to see if it fits in the specified range (digits are in 0x30-0x39). If the number is between -128 and -1 inclusive then 256 will be added and the check will be done on that. Warning
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.
When called with a string argument they will check
every character in the string and will only return
Passing anything else but a string or integer will
return
It should be noted that ctype functions are always preferred over
regular expressions, and even to some equivalent
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