Check if a value exits in array (Laravel or Php)

You can use in_array for this.

Try

$design_id = 'hc1wXBL7zCsdfMu';
$list_desings_ids = array('hc1wXBL7zCsdfMu','dhdsfHddfD','otheridshere');

if(in_array($design_id, $list_desings_ids))
{
  echo "Yes, design_id: $design_id exits in array";

}

instead array_key_exists you just type in_array this will solve your issue because if you dump your this array

$list_desings_ids = array('hc1wXBL7zCsdfMu','dhdsfHddfD','otheridshere');

output will be,

array(
   0 => hc1wXBL7zCsdfMu,
   1 => dhdsfHddfD,
   2 => otheridshere
)

so your code array_key_exists will not work, because here in keys 0,1,2 exists, So, you want to check values,so for values, just do this in_array it will search for your desire value in your mentioned/created array

Your array not have key .
try this

foreach($general_list_designs as $key_design=>$design) {
       #$desing->desing_id return me for example: hc1wXBL7zCsdfMu
       if(in_array($design->design_id, $list_desings_ids))
       $final_designs[] = $design;
 }