$a = "张先生";

$tip1 = $a.",欢迎您在慕课网学习PHP！";

$a .= ",欢迎您在慕课网学习PHP！";

    $b = "东边日出西边雨";

    $b .= ",道是无晴却有晴";

$c = "东边日出西边雨";

    $d = $c.",道是无晴却有晴";

echo  $tip1."<br /><br />";

    echo  $a."<br /><br />";

echo  $b."<br /><br />";

echo  $d."<br /><br />";