php - 如何实现for循环逻辑

Question

是否有一个简单的逻辑来实现for循环，取决于分隔符？

if $a>b for($i=a; $i>b; $i--)
else for($i=a; $i<b; $i++)

但我需要在一个循环中完成我不能做类似的事情

$start = $a<$b? $a : $b;

因为我需要循环始终从开始$a并走向$b，也许还有另一种方式？我可以有理由拒绝投票吗？我的问题还不清楚，如果您不理解问题，请不要触摸它。

Answer 1

Hope this helps

$inc = $a < $b ? 1: -1;
for ($i = $a; $i != $b; $i += $inc) {
    /* some code here */
}

Explanation:

First step is estimation of the increment meaning whether to increment or decrement $a to reach $b.

Obviously if $a < $b then increment needed or else decrement. $i += $inc is the generic statement that adds +1 or -1. Adding +1 is increment and adding -1 is decrement.

Ultimately the loop exit condition is $i != $b, hoping this condition will be met atleast once in the increment/decrement.

Answer 2

Your question contains some logical error. Although syntax is correct.

if $a<b for($i=a; $i>b; $i--)

Here, $a is smaller than b and in for loop you give condition $i>b which will never meet because $i and $a are already smaller than b. So, this loop will not run even for a single time. This is also same for else because here also loop will not execute for a single time.

Is that you want..?