php while ile nasıl üçgen çizilir

$a = 1;
$b = 1;

while ($a<=10) {
    while ($b<=$a) {
        echo "*";
        $b+=1;
    }
    echo "<br>";
    $a+=1;
}

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>";
}

$i=1;
while ($i <= 5) {
    $j=1;
    while ( $j<= $i) {
        $j++;
        echo "  *";
    }
    $i++;
    echo " </br>";
}