在PHP中用Do while循环遍历A-Z

I was trying to loop though a-z with a do while loop.
I know that I also can do that with foreach and forloop.

我试着用do while循环遍历a-z。我知道我也可以对foreach和forloop这样做。

$char = 'a';
do {
   echo $char;
   $char++;

} while ($char <= 'z');

Why is that giving the output:

为什么输出是:

abcdefghijklmnopqrstuvwxyzaaabacadaeafagahaiajakalamanaoapaqarasatauavawaxayazbabbbcbdbebfbgbhbibjbkblbmbnbobpbqbrbsbtbubvbwbxbybzcacbcccdcecfcgchcicjckclcmcncocpcqcrcsctcucvcwcxcyczdadbdcdddedfdgdhdidjdkdldmdndodpdqdrdsdtdudvdwdxdydzeaebecedeeefegeheiejekelemeneoepeqereseteuevewexeyezfafbfcfdfefffgfhfifjfkflfmfnfofpfqfrfsftfufvfwfxfyfzgagbgcgdgegfggghgigjgkglgmgngogpgqgrgsgtgugvgwgxgygzhahbhchdhehfhghhhihjhkhlhmhnhohphqhrhshthuhvhwhxhyhziaibicidieifigihiiijikiliminioipiqirisitiuiviwixiyizjajbjcjdjejfjgjhjijjjkjljmjnjojpjqjrjsjtjujvjwjxjyjzkakbkckdkekfkgkhkikjkkklkmknkokpkqkrksktkukvkwkxkykzlalblcldlelflglhliljlklllmlnlolplqlrlsltlulvlwlxlylzmambmcmdmemfmgmhmimjmkmlmmmnmompmqmrmsmtmumvmwmxmymznanbncndnenfngnhninjnknlnmnnnonpnqnrnsntnunvnwnxnynzoaobocodoeofogohoiojokolomonooopoqorosotouovowoxoyozpapbpcpdpepfpgphpipjpkplpmpnpopppqprpsptpupvpwpxpypzqaqbqcqdqeqfqgqhqiqjqkqlqmqnqoqpqqqrqsqtquqvqwqxqyqzrarbrcrdrerfrgrhrirjrkrlrmrnrorprqrrrsrtrurvrwrxryrzsasbscsdsesfsgshsisjskslsmsnsospsqsrssstsusvswsxsysztatbtctdtetftgthtitjtktltmtntotptqtrtstttutvtwtxtytzuaubucudueufuguhuiujukulumunuoupuqurusutuuuvuwuxuyuzvavbvcvdvevfvgvhvivjvkvlvmvnvovpvqvrvsvtvuvvvwvxvyvzwawbwcwdwewfwgwhwiwjwkwlwmwnwowpwqwrwswtwuwvwwwxwywzxaxbxcxdxexfxgxhxixjxkxlxmxnxoxpxqxrxsxtxuxvxwxxxyxzyaybycydyeyfygyhyiyjykylymynyoypyqyrysytyuyvywyxyyyz

instead of just:

而不是:

abcdefghijklmnopqrstuvwxyz

3 个解决方案

#1

From the documentation:

从文档:

PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in PHP and Perl $a = 'Z'; $a++; turns $a into 'AA', while in C a = 'Z'; a++; turns a into '[' (ASCII value of 'Z' is 90, ASCII value of '[' is 91). Note that character variables can be incremented but not decremented and even so only plain ASCII alphabets and digits (a-z, A-Z and 0-9) are supported.

PHP在处理字符变量而不是C的算术操作时遵循Perl的惯例。例如，在PHP和Perl中，$a = 'Z';$ + +;将$a转换为AA, C a = 'Z';+ +;将a转换为“[”(ASCII值为“Z”为90,ASCII值为“[”]为91)。注意，字符变量可以递增，但不能递减，甚至只支持普通的ASCII字母和数字(a-z、a-z和0-9)。

Try something like this:

试试这样:

for($i = 0, $char = 'a'; $i < 26; $i++, $char++) {
   echo $char;
}

#2

Because

因为

<?php

$char = 'z';

var_dump(++$char); //string(2) "aa"

var_dump('aa' <= 'z'); //bool(true)
var_dump('za' <= 'z'); //bool(false)

DEMO

演示

Personally I'd just use a loop from 97 (ascii value for a) to 122 (ascii value for z):

就我个人而言，我只是使用一个循环从97 (ascii值为a)到122 (z的ascii值):

for ($i = 97; $i <= 122; $i++) {
    echo chr($i);
}

#3

You cannot compare z with 26 or some kind of number. You need something to compare it with the number. The function ord() does it. So, you can do something like:

你不能将z与26或某种数字进行比较。你需要一些东西来和数字进行比较。函数ord()做到了这一点。你可以这样做:

$char = 'a';
do {
   echo $char;
   $char++;

} while (ord($char) <= ord('z'));

#1