PHP string increment and decrement example introduction_PHP tutorial

Today I saw this passage in the PHP manual:

"When dealing with arithmetic operations on character variables, PHP follows Perl's habits rather than C's. For example, in Perl $a = 'Z' ; $a++; will turn $a into 'AA', and in C, a = 'Z'; a++; will turn a into '[' (the ASCII value of 'Z' is 90, and the ASCII value of '[' The value is 91). Note that character variables can only be incremented, not decremented, and only support pure letters (a-z and A-Z). Incrementing/decrementing other character variables is invalid, and the original string will not change. "

That is. Say:

Copy code The code is as follows:

for($i = 'A'; $i <= 'Z '; $i++) {
echo $i;
//if( $i == 'ZZZ') die();
}

The result is: ABCDEFGHIJKLMNOPQRSTUVWXYZAAABACADAEAFAGAHAIAJAKALAMANAOAPAQARASATAUA… ………

There are also string variables that cannot be decremented:

Copy code The code is as follows:

$ a = 'Z';
--$a;
echo $a; // Z

This also shows that $a++ or ++$a cannot be $a = $a + 1; to explain

Copy code The code is as follows:

$a = $b = 'Z';
$a = $a + 1;
echo $a; //1
++$b;
echo $b; //AA

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