ob_start();
$time1 = microtime(1);

for ($j = 0; $j < 10000; $j++) {
    for($i=0;$i<10;$i++)
    { echo '1php '; }
}

$a = (microtime(1)-$time1);

$time1 = microtime(1);

for ($j = 0; $j < 10000; $j++) {
while($i<10) {
echo 'w1';
$i +=1;
}
}

$b = (microtime(1)-$time1);
ob_end_clean();

echo "A: $a, B: $b";

$a = 10; 
$b = 515; 
$c = 0.515; 
$d = $b<=$a&&$a==$c||$b>$c?0:1; 
echo $d;

$d = 0&&0 || 1?0:1; у || приоритет меньше, чем у &&
$d = 0 || 0
$d = 0