没有{？有可能使用die / echo等吗？

So, Well I was wondering, Is it possible to do this;

if($pro == true)
    echo "He's";
    echo "a";
    echo "pro.";

Or do I need to use { } ? Thanks.

It depends on your intentions. With your code

if($pro == true)
    echo "He's";
    echo "a";
    echo "pro.";

The result (if $pro is true) will be:

He'sapro.

If $pro is false it will be

apro.

If you don't want that output on false, please add the braces.

if($pro == true) {
    echo "He's ";
    echo "a ";
    echo "pro.";
}

questioner I think it's simple if else structure we all know from inception of coding.

After executing first line after IF block without bracket( '{' ), rest will be executed as it is.

if(1==1)
echo "Hi!";
echo "How are you?";

So the output of the above is: Hi! How are you? Both lines are returned.

Now if you want to separate out output then enclose else block,

if(1==1) { echo "Hi!"; } else { echo "How are you?"; }

So the output of the above is: Hi!

#SpongePablo has truly explained well.