Checks if all of the characters in the provided string, text, are alphabetic. In the standard C locale letters are just [A-Za-z] and ctype_alpha is equivalent to (ctype_upper($text) || ctype_lower($text)) if $text is just a single character, but other languages have letters that are considered neither upper nor lower case.
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.
Returns true if every character in text is a letter from the current locale, false otherwise. When called with an empty string the result will always be false.