How to write triangle with stars in Php. (*) I want to do it with while

Question

I did this with a "for" loop. How can I write this with while. Thank you for your help. I just started learning PHP.

for ($a=0; $a <=10 ; $a++) { 
    for ($y=0; $y <= $a ; $y++) { 
        echo "*";
    }
    echo "<br>";
}
for ($a=10; $a >=1 ; $a--) { 
    for ($y=1; $y <= $a ; $y++) { 
        echo "*";
    }
    echo "<br>";
}

Answer 1

The trick to rewriting a for statement to a while statement is extracting the incrementer initialization ($a = 0) and the incrementation ($a++) itself.

So

for ($a=0; $a <=10 ; $a++)

becomes

$a = 0;
while ($a <=10) {
    $a++;
}

Result

$a = 0;

while ($a <=10) {
    $y = 0;
    while ($y <= $a) { 
        echo "*";
        $y++;
    }
    echo "<br>";
    $a++;
}

$a = 10;

while ($a >=1) { 
    $y = 1;
    while ($y <= $a) { 
        echo "*";
        $y++;
    }
    echo "<br>";
    $a--;
}

Answer 2

for ($i=10; $i<80; $i+=4) {
  // do something
}

is equivalent to:

$i=10
while ($i<80) {
  // do something
   $i+=4;
}