php - Arraystring(19) Why isn't it a string and why wont it convert to one -

the following code

foreach($_post['queryvars'] $key=>$value) {             if(in_array($key,$validnames) && !isset($translation[$key])) {                 try {                     $runoptions = true;                     if(in_array($key,$datefields)) {                         if(isset($_post['queryvars'][$key.'end'])) {                             $runoptions = false;                             $prep->bindparam(":{$key}start",$_post['queryvars'][$key],pdo::param_str);                             $prep->bindparam(":{$key}end",$_post['queryvars'][$key.'end'],pdo::param_str);                         }                     }                     if($runoptions) {                         var_dump($key);                         echo "$key = ";                         var_dump($_post['queryvars'][$key]);                         echo "\n";                         $prep->bindparam(":$key",$_post['queryvars'][$key],pdo::param_str);                     }                 }                 catch(exception $ex) {                     echo $querystart." \n" ;                     echo 'error: "'.$_post['queryvars'][$key].'"'."\n";                     echo $ex->getmessage();                     echo $ex->gettrace();                 }             }         } 

throws weird notice

<b>notice</b>:  array string conversion in <b>c:\xampp\htdocs\lib\talk\getallreisfinancieel.php</b> on line <b>147</b><br /> arraystring(19) "totaalbedragfactuur" 

the var dump says arraystring, when google on array string can't find single hit of arraystring is.

i've tried making "normal" string $key = "$key"; no avail.

does know how solve or how can test if type arraystring?