You have not declared either $flip or $A before trying to use them in an expression. Also, using goto is really bad practice, there are better ways of resetting your values.
I have modified your code to the following, although I am not sure what it is supposed to do. As shown, it runs (almost) for ever.
$num = 100;
$flip = 0;
$A = 0;
while($flip <= $num) {
$flip++;
$rn = rand(0,1);
if ($rn == 0){
$flip = 0;
$A = 0;
}
$A++;
}
echo " The number of FLIPS Are: $flip <br>";
echo " The number of Number ONES Are: $A <br>";
[edit]
Here is a complete webpage with the implementation of your algorithm, without any goto statements:
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<?php
function flipper($count) {
$num = $count;
$sets = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
for ($flip = 0; $flip < $num; $flip++) {
for ($i = 0; $i < 26; $i++) {
$r = rand(0,1);
if ($r == 1) {
break;
}
$sets[$i]++;
}
}
for ($i = 0; $i < 26; $i++) {
echo '$sets[' . $i . "]: $sets[$i]" . '<br>';
}
}
flipper(1000);
?>
</body>
</html>
[/edit]