how can be write php inside the laravel's blade page?

i write like this but did not got the output.

@php
  @if(isset($value['0']['cmsg'])) 
    $cmsg = json_decode($value['0']['cmsg']);
  @endif
  @if(isset($value['0']['cmsgerr'])) 
    $cmsgerr = json_decode($value['0']['cmsgerr']);
  @endif
@endphp

via Chebli Mohamed