为什么ctype_alpha不将整数-128到255识别为字母，如果它们是数组的一部分？

Question

Why do these return true:

ctype_alpha(74); // returns true $bar = 74; ctype_alpha($bar); // returns true

but this returns false:

$foo = [1,2,3,'74']; ctype_alpha($foo[3]); // returns false

Answer 1

Of the numeric values in your test array, only 74 is the ASCII code of a letter (J), but you have supplied that as a string, not an integer, so it will not be interpreted as a character. The integers 128, 127, and 64, do not correspond to any letters, which is why ctype_alpha returns false for those. When you supply 74 as an integer value, then it does return true. ctype_alpha is working fine.