PHP: Loop through multidimensional array and remove html tags

I want to loop through an multidimensional array, which has multiple keys and arrays of strings assigned to the keys. For each string in the arrays, I want to execute the strip_tags function and replace the old string with the new one.

I am very new to php and I am very confused.

So thanks for your help!

EDIT:

This is what I did so far:

<?php
include ('../db.php');


$sql = "select id, post_title, post_content, post_type, post_date from wp_posts where post_type = 'post' order by post_date desc limit 20";
$ergebnis = $db->query($sql);

$zeile = $ergebnis->fetchALL(PDO::FETCH_ASSOC);

$keys = array_keys($zeile);

$valuearray = array();


for($i=0; $i < count($keys); $i++) {

    foreach($zeile[$keys[$i]] as $key => $value) {
    if(is_string($value) == true) {
        $value1 = strip_tags($value);
        array_push($valuearray, $value1);
        $zeile[$keys[$i]] = $valuearray;
     }
    else {
        array_push($valuearray, $value);
        $zeile[$keys[$i]] = $valuearray;        
        }
 }
}
    


$json = json_encode($zeile);

echo $json;

?>

I need the output as json for flutter development.