I believe ryan_vietnow meant ($variable21=="") instead of ($variable21="") . It may not fix your problem, but == is used to compare a variable to a value or to another variable. = is used to assign a value to a variable. Don't get is equal to (==) confused with equals(=). You could also try:
if(empty($variable21)){
echo "Meeting time is not yet determined. Please check again later.";
}
else{
echo "<p<b>Meetings:</b> $variable21</p>";
}If all else fails, use strlen to check the strings length aka the number of characters in the string assigned to the variable:
if(strlen($variable21)>1){
echo "<p<b>Meetings:</b> $variable21</p>";
}
else{
echo "Meeting time is not yet determined. Please check again later.";
}