PHP代码背后的逻辑

Question

I'm having trouble understanding the logic behind the following code:

Initial code

            <?php
            $output_arr=array();
            $handle = fopen("../etc/init.d/bandwidthlimiters/rulestest", "r");
            if ($handle) {

                $i=1;
                while (($line = fgets($handle)) !== false) {

                $test_string=$line;
                $test_string=str_replace(" htb rate ","@@",$test_string);
                $test_string=str_replace("kbit ceil ","@@",$test_string);

                $tmp = explode("@@", $test_string);
                array_push($output_arr,$tmp[1]);
                $i++;
               }

                fclose($handle);
            } else {
                // error opening the file.
            } 

            echo $output_arr[5]
            ?>

At the moment echo $output_arr[5] provides a printed value of "5" when taken from the file source listed. File contents shown below, under "New Output".

New Output

Instead of looking for values between " htb rate " and "kbit ceil", I would like it to grab results based on the following terms: " ceil " and "kbit"

tc class add dev br-lan parent 1:1 classid 1:2 htb rate 1kbit ceil 11111kbit
tc class add dev br-lan parent 1:1 classid 1:3 htb rate 2kbit ceil 22222kbit
tc class add dev br-lan parent 1:1 classid 1:4 htb rate 3kbit ceil 33333kbit
tc class add dev br-lan parent 1:1 classid 1:5 htb rate 4kbit ceil 44444kbit
tc class add dev br-lan parent 1:1 classid 1:6 htb rate 5kbit ceil 55555kbit

By using the sample lines above, the new result should retrieve "55555", instead of the original "5"

Modified version

I have tried a modification, as shown below:

                $test_string=str_replace(" ceil ","@@",$test_string);
                $test_string=str_replace("kbit","@@",$test_string);

However, this does not return any result. For future use, I would like to be able to manipulate this further to return different results again, in which case, any explanation of how to use this method would be appreciated.

Answer 1

Your modification is resulting in this value of $test_string:

tc class add dev br-lan parent 1:1 classid 1:6 htb rate 5@@@@55555@@

Notice that there are two @@ sequences before the field that you want to retrieve. The first comes from replacing kbit, the second comes from replacing ceil. When you explode it, you get:

array(4) {
  [0]=>
  string(57) "tc class add dev br-lan parent 1:1 classid 1:6 htb rate 5"
  [1]=>
  string(0) ""
  [2]=>
  string(5) "55555"
  [3]=>
  string(1) "
"
}

So 55555 is in $tmp[2], not $tmp[1].