please someone can explain me in detailed way how this loop in php works?
for($a=1;$a<10;$a++)
{
echo "<br>";
for ($b=0;$b<$a;$b++)
echo $a;
}
Why the output is 1 22 333 4444 55555 etc and not just 1 2 3 4 5 and so on, i know is something elementary but i cannot get it.
thank you.
The key is the $a in the inner loop.
for ($b=0;$b<$a;$b++)
^-------------- HERE
this will count from zero to $a (which is increased every time) in every loop and output $a as many times.
$a = 0: no output (inner loop runs from 0 to 0)
$a = 1: 1 output (inner loop runs from 0 to 1)
$a = 2: 2 outputs (inner loop runs from 0 to 2)
$a = 3: 3 output (inner loop runs from 0 to 3)
etc.....
There are two loops in your code, the outer loop initialize the value of $a as 1
$a = 1;
Then in the inner loop $b is set to 0
$b = 0;
The condition for the inner loop to succeed in its first execution is
$b < $a
Or if you don't follow it,
0 < 1
Because remember the inner loop initialize $b as 0, and $a is initialized in the outer loop as 1
So 0 is less that 1, so it will succeed and execute
echo $a; // 1
The inner loop will only execute it 1 time because in its second iteration $b is already 1
$b++
Now it will go to the outer loop again, and $a will equal to 2 because the for loop just did
$a++
2 is less than 10 so it will execute the second loop again. But now the second loop is condition changes because
$b < $a // 0 < 2
Because remember $a is now equal to 2! So the condition succeed and it will execute
echo $a // or 2
Then after executing in its first try, the for loop will do $b++ so $b will become 1.
SO now, the for loop will test the condition again and the result will be
$b < $a // 1 < 2
1 is less than 2 so it will execute the echo statement again
echo $a // 2
Hence you get 22
Then after that the for loop will do $b++, so now $b is 2 already! Because 2 is not less than 2, hence it will fail and go to the outer loop again.
Each time through the outer loop, the inner loop is performed a times. So 1 is echoed once, 2 is echoed twice, and so on.
1 2 3 4 5?