使用条件函数停止PHP while循环

Question

I'm using the following functions to get the final URL from a series of redirects...

https://stackoverflow.com/a/4102293/1183476

It works great 99.8% of the time. I can't really pinpoint the exception, but I believe it has something to do with the server on the other end generating a new random URL for each visit. Thus, this script gets stuck in an infinite loop.

To replicate the issue replace the get_redirect_url function with...

function get_redirect_url($url){
    return $url.'x';
}

The Question

How can I set a time or iteration limit?

I feel like I've tried everything. I tried putting a time based condition in the while loop that looks for the next URL, but its not working and I don't know why. Like this...

function get_all_redirects($url){
    $redirects = array();
    $start = time();
    while ($newurl = get_redirect_url($url) && time()-$start < 10 ){
        if (in_array($newurl, $redirects)){
            break;
        }
        $redirects[] = $newurl;
        $url = $newurl;
    }
    return $redirects;
}

I also tried counting iterations like this...

function get_all_redirects($url){
    $redirects = array();
    $i = 0;
    while ($newurl = get_redirect_url($url) && $i < 10 ){
        if (in_array($newurl, $redirects)){
            break;
        }
        $redirects[] = $newurl;
        $url = $newurl;
        $i++;
    }
    return $redirects;
}

The examples above are just 2 of many failed attempts. I'm ready for help. Thanks in advance.

Answer 1

Just scanning (for a second) your code does not show any obvious problems but I would like to make some suggestions.

Whenever I see conditionals in control flow statements that use the result of an assignment it always smells fishy (ok, lets say its not my style):

while ($newurl = get_redirect_url($url) ...

I could bet that by yanking out that assignment/condition or whatever you want to call it, your code will become more readable and maintainable and by some happy chance fix the issue you are seeing.

Answer 2

I am assuming, the loop you are talking of is a real loop, thus the iteration would not work, because of the break here breaks before incrementing if the url is in the array already.

if (in_array($newurl, $redirects)){
    break;
}

Why the timer doesn't work, I dont know. But fixing the incrementing by putting that $i++; at the top of the loop should at least improve your situation.

Answer 3

There is a problem in the while :

while ($newurl = get_redirect_url($url) && time()-$start < 10 )

and some parens should be added around $newurl = get_redirect_url($url)

while ( ($newurl = get_redirect_url($url)) && time()-$start < 10 )

instead, since && has higher precedence than = . Otherwise $newurl gets the result of the conditional expression get_redirect_url($url) && time()-$start < 10 which is 1 .