使用PHP在一行中写两条或更多条指令

I have a very simple question for you guys. After deep researches, I've found nothing useful to get a good answer.

I just really like to know the way to write multiple instructions/commands in the same line, with PHP. Just to be clear, this:

<?php
  if (true) {
    echo "First,";
    echo " second";
    echo " and third.";
  }
?>

shoud become this:

<?php
  if (true)
    echo "First," & echo " second" & echo " and third";
?>

So, the script above can execute three operations in one line of code. I tried to use the "&" sign to append more instructions in the same line and it seems it works... Is this the correct way to do what I want to do? May this cause any problems?

Thanks!

PS: the "echo" instruction is just as example (I know that you can merge strings just using the dot (.) sign

PHP puts no significance on a line break at all. All you need to do is remove the line break, everything else can stay exactly the same:

<?php if (true) { echo "First,"; echo " second"; echo " and third."; } ?>

The statements are already terminated and separated by ;.

No. It's not correct. echo is not a function, and is not something you can & together like that. It does, however, support comma-separated "arguments", so something like

echo 'first', 'second', 'third';

is entirely possible and totally valid PHP code.

Even if the & version was possible, you'd actually be LOSING efficiency, because you're doing 3 echo calls, and then trying to combine their non-existence return values. e.g. you'd be turning 3 operations into 5.