Comma Separated Strings

Convert comma separated string to array and test for entries

Ensure no trailing comma that will produce a blank final array entry
  $MyCommaSeperatedString = "abc,def,ghi,";

  //Ensure there is no trailing comma
  $MyCommaSeperatedString = rtrim(trim($MyCommaSeperatedString), ",");
  $MyArray = ($MyCommaSeperatedString === '') ? [] : explode(',', $MyCommaSeperatedString);
  //(No commas will result in the text in the string being in an array of length 1, an empty string will result in an empty array)

  print_r($MyArray);

  //$MyCommaSeperatedString = "abc,def,ghi,";
  //Will output: Array ( [0] => abc [1] => def [2] => ghi )

  //$MyCommaSeperatedString = "";
  //Will output: Array ()
Examples
  $MyCommaSeperatedString = "abc,def,ghi";
  $MyArray = ($MyCommaSeperatedString === '') ? [] : explode(',', $MyCommaSeperatedString);
  print_r($MyArray);
  //Will output: Array ( [0] => abc [1] => def [2] => ghi ) 
    

  $MyCommaSeperatedString = "abc,def,ghi,";
  $MyArray = ($MyCommaSeperatedString === '') ? [] : explode(',', $MyCommaSeperatedString);
  print_r($MyArray);
  //Will output: Array ( [0] => abc [1] => def [2] => ghi [3] => )
    

  $MyCommaSeperatedString = rtrim(trim("abc,def,ghi,"), ",");      //Ensure there is no trailing comma
  $MyArray = ($MyCommaSeperatedString === '') ? [] : explode(',', $MyCommaSeperatedString);
  print_r($MyArray);
  //Will output: Array ( [0] => abc [1] => def [2] => ghi )

Convert array into comma separated string

    $MyArray = array();
    $MyArray[] = 'abc';
    $MyArray[] = 'def';
    $MyArray[] = 'ghi';
    $MyCommaSeperatedString = implode(',', $MyArray);      //Convert array to comma seperated string
    echo $MyCommaSeperatedString . "<br>";
    //Will output: abc,def,ghi

Add new value to a comma separated string

    if ($MyCommaSeperatedString  === '')
      $MyCommaSeperatedString  = $MyNewValue;
    else
      $MyCommaSeperatedString  .= ',' . $MyNewValue;