Nested loops

[jasmin0510]

Hi guys and Marry Christmas to all of you who are celebrating!

I'm traying to learn PHP on my own and I am stuck in traying to understand this concept of nested loops and using break/continue in them.

 So, can someone please explain to me how this code below is working and why I'm getting result that I don't expect.

Code is: 

for($i = 0; $i < 6; $i++) { 
    for($d = 0; $d < 4; $d++) { 
        if($d == $i) { 
            continue 2;
        }
        echo $d."d <br>";
        echo $i."i <br>";
        
        
    }
    
} 

When I was writing this code I was expecting that result, because of continue 2, will be 4i and 5i. But instead of that I got this 0d,1i,0d,2i,1d,2i,0d,3i,1d,3i,2d,3i,0d,4i,1d,4i,2d,4i,3d,4i,0d,5i,1d,5i,2d,5i,3d,5i. 

I really want to how I got this result, I spent whole day traying to explain this to myself and failed miserably.

 

[Barand]

"continue" says "Stop processing this iteration and continue with the next. Just a single "continue (1)" would take you to the start of the inner loop and start with the next value of $d. Because you have "continue 2" it goes to the start of the outer loop and continues with the next value of $i.

[jasmin0510]

2 hours ago, Barand said:

"continue" says "Stop processing this iteration and continue with the next. Just a single "continue (1)" would take you to the start of the inner loop and start with the next value of $d. Because you have "continue 2" it goes to the start of the outer loop and continues with the next value of $i.

Thank you for this answer. 

Yeah, I understand that basic concept of continue and continue 2. But the results that I'm getting in this example are beyond my understanding and expectations. 

In first iteration $i = 0 and $d = 0, so the condition in if is TRUE and continue 2 is stopping further execution of code in this first iteration for both for loops, meaning that those two echo lines are not executed. So the iteration number 2 begins and now $i = 1 and $d = 1 and again condition in if is TRUE and continue is stopping that iteration. 

This is my understanding of things. What I don't understand is how I'm getting  this: 0d,1i,0d,2i,1d,2i,0d,3i,1d,3i,2d,3i,0d,4i,1d,4i,2d,4i,3d,4i,0d,5i,1d,5i,2d,5i,3d,5i.

I tried to resolve this with trace tables but that didn't help me. ☹️

[Barand]

Get a pencil and read through the code line by line as if it were being executed.

For each iteration, note the values of i and d and the values that would be output.

You should get this (try it yourself before peeping)

ITERATIONS
 -----+------+---------
 i      d       Ouput
 -----+------+---------
 0      0        continue to next i
        1
        2
        3
 1      0        0d 1i      
        1        continue to next i
        2
        3 
 2      0        0d 2i
        1        1d 2i      
        2        continue to next i
        3
 3      0        0d 3i
        1        1d 3i
        2        2d 3i      
        3        continue to next i
 4      0        0d 4i
        1        1d 4i
        2        2d 4i
        3        3d 4i
 5      0        0d 5i
        1        1d 5i
        2        2d 5i
        3        3d 5i
 

[jasmin0510]

44 minutes ago, Barand said:

Get a pencil and read through the code line by line as if it were being executed.

For each iteration, note the values of i and d and the values that would be output.

You should get this (try it yourself before peeping)

 

  Reveal hidden contents

 

ITERATIONS
 -----+------+---------
 i      d       Ouput
 -----+------+---------
 0      0        continue to next i
        1
        2
        3
 1      0        0d 1i      
        1        continue to next i
        2
        3 
 2      0        0d 2i
        1        1d 2i      
        2        continue to next i
        3
 3      0        0d 3i
        1        1d 3i
        2        2d 3i      
        3        continue to next i
 4      0        0d 4i
        1        1d 4i
        2        2d 4i
        3        3d 4i
 5      0        0d 5i
        1        1d 5i
        2        2d 5i
        3        3d 5i
 

 

 

 

You really got me motivated, and I was in despair. I told my self - if this man thinks that I should try again than I will do it. I just reduced the number of iterations, make trace table and I had that moment of revelation😄

I didn't look up your hidden content in post, and I am glad that I didn't. 

Thank you very much. Have a wonderful holidays.🤗

 

Edited December 25, 2020 by jasmin0510