转换字符; 像A到B，B到C，

I want to have a short and easy way to replace character:
A to B, B to C, Z to A, ... in PHP.

I already have tried this:

$pwd = "Abc";
for($char = ord('A'); $char <= ord('Z'); $char++) {
  $newc = $char+1;
  if($newc > 90)
    $newc = 65;
  $pwd = str_replace(chr($char), chr($newc), $pwd);
  $pwd = str_replace(chr($char+32), chr($newc+32), $pwd);
}
echo $pwd;

But when I use it I only get "Aaa"...

$str = 'a';
echo ++$str; // prints 'b'

This should work for you:

Here I simply str_split() the string into an array and then go through each character with array_map(). There I check if it is either a lowercase or an uppercase letter.

If yes I simply return the character incremented and if it goes over zZ I just return aA.

At the end I simply implode() the array again into a string.

<?php

    $str = "Aac";

    $str = implode("", array_map(function($v){
        if(ord($v) >= 65 && ord($v) <= 90)
            return (++$v > 90 ? char(65) : $v);
        elseif(ord($v) >= 97 && ord($v) <= 122)
            return (++$v > 122 ? char(97) : $v);
        else
            return $v;
    }, str_split($str)));

    echo $str;

?>

output:

Bbd

Here is a simple loop that does the job:

// A function to replace uppercase characters in a string with
// the next letter in the alphabet

function replace($str) {
    $len = strlen($str);

    for ($i = 0; $i < $len; ++$i) {
        // Check if the current character is an uppercase letter

        if (ctype_upper($str[$i])) {
            if ($str[$i] == 'Z') {
                // If it is a "Z", simply make it an "A"

                $str[$i] = 'A';
            }
            else {
                // If it is anything else, just get the next
                // character from the ASCII table

                $str[$i] = chr(ord($str[$i]) + 1);
            }
        }
    }

    return $str;
}

You can use it like this:

echo replace('HELLO, YOU! ABCDEFGH...XYZ');

This will output IFMMP, ZPV! BCDEFGHI...YZA as expected.

You can read more about ctype_upper here: http://php.net/ctype-upper - it is basically a function to check whether a string or a character is uppercase or not.

chr and ord just convert an ASCII code to a character and vice-versa. Read the official documentation if necessary: http://php.net/ord and http://php.net/chr.