PHP remove the last character from my loop - php

Question

I'm writing a string from my form and I'd like to remove the last comma from the end. I understand that I can use the rtrim(), but I don't understand how I can return a variable from my loop. I'm sure this is an easy answer, just super confused. Thanks!
if (isset($_POST['submit'])) {
foreach ( $_POST['data'] as $data )
{
echo $data['Monday'];
echo $data['Tuesday'];
echo $data['Wednesday'];
echo $data['Thursday'];
echo $data['Friday'];
echo $data['Saturday'];
echo $data['Sunday'];
echo ", ";
}
} // end if

Answer 1

You can check if you are on the last element and skip printing the comma if so:
end($_POST['data'); // fast forward to the end of the array
$lastKey = key($_POST['data'); // and remember what the last key is
foreach ( $_POST['data'] as $key => $data )
{
echo $data['Monday'];
echo $data['Tuesday'];
echo $data['Wednesday'];
echo $data['Thursday'];
echo $data['Friday'];
echo $data['Saturday'];
echo $data['Sunday'];
if ($key !== $lastKey) echo ", ";
}
This approach feels cleaner to me: prevention is better than treatment.

Answer 2

you need to have a variable
$str = null;
if (isset($_POST['submit'])) {
foreach ( $_POST['data'] as $data )
{
$str .= $data['Monday'] .
$data['Tuesday'] .
$data['Wednesday'] .
$data['Thursday'] .
$data['Friday'] .
$data['Saturday'] .
$data['Sunday'] .
", ";
}
$str = substr($str,0,-2);
}
Then you have the data in $str which you can then echo or do stuff with

Answer 3

You could get the last index of the $_POST['data'] and simply not echoing a , when that's reached:
end($_POST['data']);
$last_key = key($_POST['data']);
foreach ($_POST['data'] as $key => $data) {
// echoes here
if ($key != $last_key) {
echo ',';
}
}

Answer 4

Instead of echo'ing the data immediately, store it in a buffer...
if (isset($_POST['submit'])) {
$buffer = "";
foreach ( $_POST['data'] as $data )
{
$buffer .= $data['Monday'];
$buffer .= $data['Tuesday'];
$buffer .= $data['Wednesday'];
$buffer .= $data['Thursday'];
$buffer .= $data['Friday'];
$buffer .= $data['Saturday'];
$buffer .= $data['Sunday'];
$buffer .= ", ";
}
$buffer = rtrim($buffer, ", ");
echo $buffer;
} // end if
Or, even shorter:
if (isset($_POST['submit'])) {
implode(", ", $data);
} // end if
Assuming $data only has those Monday-Sunday keys..