<?php
$a= 1;
$b= 2;
$c= 3;
echo "$a+$b","$a+$c"; //1+21+3;
echo "$a+$b"."$a+$c"; // 1+21+3;
echo $a+$b,$a+$c; // 34;
echo $a+$b.$a+$c; // 34;
function tect(){
echo '2222';
}
echo '111',tect().'3333'; //11122223333;
echo '111'.tect().'3333';// 22221113333;
?>