Foreach loop inside a Group related options with <optgroup>

Question

I have an array

$this->getprevioussprint = Array

( [0] => Array ( [release_name] => Relese1 [sprint_name] => Sprint1 [sprint_id] => 1 )

[1] => Array
    (
        [release_name] => Relese1
        [sprint_name] => Sprint2
        [sprint_id] => 2
    )

[2] => Array
    (
        [release_name] => v2
        [sprint_name] => Sprint1
        [sprint_id] => 3
    )

)

I have a Foreach loop inside a Group related options with so i tried

<select class="col-md-2">
    <?php foreach ($this->getprevioussprint as $key =>$pSprint):
    $prev=$pSprint['release_name'];
    ?>
    <optgroup label="<?php echo  $pSprint['release_name'] ;  ?>">
        <option value=""><?php echo $pSprint['sprint_name'] ?></option>
    </optgroup>
</select>

but i got output

 <select>
        <optgroup label="release_name">
            <option value="1">Sprint1</option>
        </optgroup>
        <optgroup label="Relese1">
            <option value="2">Sprint2</option>
        </optgroup> 
 <optgroup label="V2">
            <option value="3">Sprint1</option>
        </optgroup> 
    </select>

expected output

 <select>
        <optgroup label="Relese1">
            <option value="1">Sprint1</option>
            <option value="2">Sprint2</option>
        </optgroup> 
 <optgroup label="v2">
            <option value="3">sprint1</option>

        </optgroup> 
    </select>

Any help would be greatly appreciated

Answer 1

First you need to grouping arrays. Mean array with same release_name putted in one array. So use

$newArr = [];
foreach ($_this->getprevioussprint as $item){
    $newArr[$item['release_name']][] = $item;
}

Then loop through new array

<select class="col-md-2">
    <?php foreach ($newArr as $key=>$item): ?>
    <optgroup label="<?= $key ?>">
        <?php foreach ($item as $key=>$pSprint): ?>
        <option value=""><?= $pSprint['sprint_name'] ?></option>
        <?php endforeach ?>
    </optgroup>
    <?php endforeach ?>
</select>

Answer 2

you need to group the arrays with their release name at first:

echo '<select class="col-md-2">';

    foreach (group_by_release_name($this->getprevioussprint) as $key => $val):

        echo '<optgroup label="'.$key.'">';

        foreach($val as $k => $v):

            echo '<option value="'.$v['sprint_id'].'">'.$v['sprint_name'].'</option>';

        endforeach;

        echo '</optgroup>';

    endforeach;

echo '</select>';

function group_by_release_name($arr){

    $result = [];

    $current_release_name = '';

    foreach($arr as $k => $v){
        $current_release_name = $v['release_name'];

        unset($v['release_name']);

        $result[$current_release_name][] = $v;
    }

    return $result;
}