illegal offset type in php on vscode no error, but on page says that error

hello i’m running into a problem, it says on the browser illegal offset type,
im declaring an array this way:

 $matriculas = [
        1 => ["99-99-99", "D"],
        2 => ["88-88-88", "D"],
    ];

and the error is in this line :

 $series[$option] = [$option['matricula'],$option['type']];

the function looks like this:

<?php 
    $query ="SELECT * FROM matriculas";
    $result = $con->query($query);
    if($result->num_rows> 0){
      $options= mysqli_fetch_all($result, MYSQLI_ASSOC);
    }
    $series = array();
    foreach ($options as $option) {
        $series[$option] = [$option['matricula'],$option['type']];
    }
?>
<select name="id">
   <option>Select matricula</option>
<?php 
  foreach ($series as $ID => $values) {
?>
    <option name=<?php $ID ?> > <?php echo $values[0]; ?></option>
<?php 
}
>
</select>

how can i make it right? thanks in advance for your help

>Solution :

It’s almost right.

Based on the subsequent foreach ($series as $ID => $values), I think you want this instead:

foreach ($options as $option) {
    $series[$option['id']] = [$option['matricula'], $option['type']];
}

But unless you’re going to use the $option['type'] value for something else later, it could be simplified to

foreach ($options as $option) {
    $series[$option['id']] = $option['matricula'];
}