http://localhost/6-4.php

 ECHO say hello!!
print say hello!!
print say how are you?

---

1:msg变量的内容是I am fine.
2:msg变量的内容是$msg
I am fine.

<?php
echo "ECHO say hello!!<br>";
print "print say hello!!<br>";
print ("print say how are you?<br>");
$msg="I am fine.";
echo "<hr width=50%>";
echo "1:msg变量的内容是$msg<br>";
echo '2:msg变量的内容是$msg<br>';
echo $msg;
?>