php - How to insert value key-value pair in array -

i'm trying insert value key pair in array in php. code given below issue is giving error illegal offset type on line i'm trying push data. $request_url data coming api.

$response = simplexml_load_file($request_url); //make different array of images of small , medium , large size $array_features = array(); $array_smallimages = array(); $array_mediumimage = array(); $array_largeimage = array();  foreach($response->items->item $item){     echo $item->itemattributes->title.'<br>';        echo $item->asin.'<br>';     $asin = $item->asin;     echo $item->detailpageurl.'<br>';     echo $item->itemattributes->manufacturer.'<br>';     $small_img = $item->smallimage->url;     $array_smallimages[$asin] = $small_img;      //$array_smallimages =  $item->smallimage->url;     echo $item->mediumimage->url.'<br>';     echo $item->largeimage->url.'<br>';     //echo $item->itemattributes->manufacturer.'<br>';       echo 'features:'.'<br>';     foreach($item->itemattributes->feature $fea){     //  $array_features[$item->asin] = $fea;         echo $fea.'<br>';     } 

$array_smallimages[$asin] = $small_img; line on error coming warning: illegal offset type

illegal offset type errors occur when attempt access array index using object or array index key

use trim($asin) before $array_smallimages[$asin] = $small_img;