Print multi select option with comma in php

Using php we can print or display multiple select option with comma.
Copy this php code and test.
<form action="<?=$_SERVER['PHP_SELF']?>" method="post">
<select name="test[]" multiple="multiple">
<option value="one">one</option>
<option value="two">two</option>
<option value="three">three</option>
<option value="four">four</option>
<option value="five">five</option>
</select>
<input name="submit" type="submit" value="Send" />
</form>
<?php
function comma($arr){
$length=count($arr);
if($length>=1)
{
$i=0;
foreach($arr as $key=>$value)
{
$i++ ;
if($i!=$length)
$itemid=$itemid.''.$value.', ';
if($i==$length)
$itemid=$itemid.''.$value;
}
}
return $itemid;
}
if(isset($_POST['submit'])){
if($_POST['test']!=''){
//sort($_POST['test']);
$country=comma($_POST['test']);
echo $country;
}
}
?>

php print statement

two basic contsructer for printing the outputs are echo and print. It prints only one arguments

code is:
print "Hello World";
or echo "Hello";