$teststring = '"Hello" and "Goodbye."';
$greedyresult = preg_replace('/".*"/', '"***"', $teststring);
$nongreedyresult = preg_replace('/".*?"/', '"***"', $teststring);
echo "Original: $teststring\n";
echo "Greedy Replace: $greedyresult\n";
echo "Non-Greedy Replace: $nongreedyresult\n";
?>