intval() And Its Arguments¶
What is happening here? Multiple things to unfold, actually.
The first line is a classic intval() call, which tries to convert a string (or almost anything else), into its decimal equivalent. Here, the conversion stops at A, because it is not a number.
The second line is a less classic intval: the second argument is the numeric base for conversion. Here, with 11, it means that the next number is A, or a. So, the result is 10 + 1 * 11 = 21.
The third line raise the numeric base. While A is still 10, the 1 is now 21, so total is 10 + 1 * 21 = 31. Of course, hexadecimal is supported, with the base 16.
We can raise the numeric base until the last letter, Z : the second argument maxes out at 10 + 26 = 36. There, the string is converted to 1691.
Beyond 36, there is no more available letters in the alphabet, so PHP just silently stops.
Finally, note that providing an integer to intval() has the same value returned as a result, whatever the numeric base. As a string, it is converted.