Detailed analysis of PHP's incremental operation on strings

When dealing with arithmetic operations on characters variables, PHP follows Perl's habits instead of C's.

A classmate asked a question:

Copy code The code is as follows:

<?php 
for($i = &#39;A&#39;; $i <= &#39;Z&#39;; $i++) { 
echo $i; 
}

What is the output?

The output is:

ABCDEFGHIJKLMNOPQRSTUVWXYZAAABACADAEAFAGAHAIAJAKALAMANAOAPAQARAS…….

Why?

It’s actually very simple. There are also instructions in the PHP manual, but I’m afraid many people don’t know how to follow each chapter. Please read the manual carefully:

PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in Perl 'Z'+1 turns into 'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ). Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

When dealing with arithmetic operations on character variables, PHP follows Perl's habits rather than C's. For example, in Perl 'Z'+1 will get 'AA', while in C, 'Z'+1 will get '[' (ord('Z') == 90, ord('[') == 91). Note that character variables can only be incremented, not decremented, and only pure letters (a-z and A-Z) are supported.

In other words, if:

the code is as follows:

$name = "laruence"; 
++$name; //将会是"laruencf"

and:

the code is as follows:

$name = "laruence"; 
--$name; //没有影响, 还是"laruence"

So, the reason for this problem is that when $i = Z, ++$i becomes AA, and when comparing strings ,
AA, BB, XX all the way to YZ Less than or equal to Z... so..

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