Untitled

Php for nested loop
for($a=1;$a<10;$a++)
{
    echo "<br>";

    for ($b=0;$b<$a;$b++)
    echo $a;

}

for ($b=0;$b<$a;$b++)
             ^-------------- HERE

$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.....

$a = 1;

$b = 0;

$b < $a

0 < 1

echo $a; // 1

$b++

$a++

$b < $a // 0 < 2

echo $a // or 2

$b < $a // 1 < 2

echo $a // 2