Multiple nested loop - php

Question

Can anyone explain me the working of multiple nested loops with some suitable example in php?
Actually, i know that how the loop inside another loop works but i don't know about how the loop inside the loop of another loop works.
For example i am trying to understand the code given below but unable to understand it's working.
<?php
for($i=5;$i>=1;$i--){
for($k=6;$k>=$i;$k--){
echo " ";
}
for($j=1;$j<=$i;$j++){
echo "* ";
}
echo "<br>";
}

Answer 1

Try to debug the flow yourself:
The main loop $i will looping for 5 times (5 to 1). For each $i the inner first loop $k will looping for various times depending on the condition and same for the next loop. Check the Result and debug yourself.
for($i = 5; $i >= 1; $i--){
echo '$i with $k Started:<br/>';
for($k = 6; $k >= $i; $k--){
echo $i." - ".$k."<br/>";
}
echo '<br/><br/>';
echo '$i with $j Started:<br/>';
for($j = 1; $j <= $i; $j++){
echo $i." - ".$j."<br/>";
}
echo "<br/>";
}
Result:
$i with $k Started:
5 - 6
5 - 5
$i with $j Started:
5 - 1
5 - 2
5 - 3
5 - 4
5 - 5
$i with $k Started:
4 - 6
4 - 5
4 - 4
$i with $j Started:
4 - 1
4 - 2
4 - 3
4 - 4
$i with $k Started:
3 - 6
3 - 5
3 - 4
3 - 3
$i with $j Started:
3 - 1
3 - 2
3 - 3
$i with $k Started:
2 - 6
2 - 5
2 - 4
2 - 3
2 - 2
$i with $j Started:
2 - 1
2 - 2
$i with $k Started:
1 - 6
1 - 5
1 - 4
1 - 3
1 - 2
1 - 1
$i with $j Started:
1 - 1

Answer 2

for($i=5;$i>=1;$i--){ // means this loop will start from i=5 and run till i >= 1
for($k=6;$k>=$i;$k--){ // now this loop will starts from 6 and run till k > i ex. in first loop k will run for k=6 and k=5
echo " ";
}
for($j=1;$j<=$i;$j++){ // this loop will starts from 1 and run till j <= i value
echo "* ";
}
echo "<br>";
}
Output:
i = 5
k=6 "&nbsp";
k=5 "&nbsp";
k = 4 // now terminate as k >= i false
j = 1 "*&nbsp";
j = 2 "*&nbsp";
j = 3 "*&nbsp";
j = 4 "*&nbsp";
j = 5 "*&nbsp";
j = 6 // now terminates as j <= i false
i = 4
so on .....