cakephp - Cakephp pdf画像変換の問題

Question

これを置く方法:

 WWW_ROOT."images".DS."uploaded_files".DS."research".DS. $pdfname;

この中に

  exec("convert -scale  1500x1000 " . escapeshellarg(BASE_URL."app/webroot/images/uploaded_files/research/${dirname}/img%d_".$pdfname.".png"));

BASE_URLを置き換えます。"app/webroot/images/uploaded_files/research/${dirname}/