如何在下拉列表中围绕php数组值包装optgroup标签

Question

I have an array called $selection that contains ascending time values from 09:00 to 18:00 in 15 minute intervals.

eg: $selection = array(09:00, 09:15, 09:30, 09:45, 10:00, 10:15, 10:30);

Some intervals could be missing, because this array is generated from some prior code which determines which times are available from google calendar (amongst other things). 09:00 isn't always the start time, sometimes the entire morning could be booked out.

I am using this array to create a drop down list.

foreach($selection as $slot) {
  if ( $slot == $selection[0] ) {
    print '<option value="'.$slot.'" selected="selected">'.date('H:i',  strtotime($slot)).'</option>';
  } else {
    print '<option value="'.$slot.'">'.date('H:i', strtotime($slot)).'</option>';
  } // end else
}

Problem

I am trying to add

<optgroup label="Morning"> .. </optgroup>

and

<optgroup label="Afternoon"> .. </optgroup>

Not sure how to do this. I have come to the conclusion that I need a while loop. Perhaps even adding extra information into the array before running the foreach loop.. not sure!

Would appreciate any help

Answer 1

For sorted array:

$interval = '';
$prev_interval = '';

foreach($selection as $slot) 
{
    // Check if selected option

    $sel = ( $slot == $selection[0] ) ? ' selected = "selected" ' : '';

    // Set optgroup interval; 
    // for HH:MM we can use basic string alphabet comaparsion

    if ($slot > '22:00')
    {
       $interval = 'Night';
    } 
    else if ($slot > '18:00')
    {
       $interval = 'Evening';
    }
   ...

    // check if interval has changed

    if ($prev_interval != $interval)
    {  
       // check if previous intrval was set

       if ($prev_interval!='') {  echo "</optgroup>" };

       printf('<optgroup label="%s">',$interval); 
    } 

    printf('<option value="%s"%s>%s</option>',$slot,$sel,date('H:i',  strtotime($slot)))  ;

    $prev_interval = $interval;
}

// last close element

if ($interval!='') { echo '</optgroup>'; } 

If the array can't be sorted before, simply store to 2D array while loop and print after.