Catchable fatal error: Object of class OCI-Lob could not be converted to string

Question

I have return some code, which returns clob data from database and here I'm trying to display it in front end and ended up in getting some error.

Below is my function which returns data

Function tabledetails() {

    $sql = "my_query";

    $std = oci_parse($conn, $sql) ;

    oci_execute($std) ;

    While(oci_fetch($std)) {

        $sdeQuery = oci_result($std, 'attribute_name') ;

    }

    return array($sdeQuery) ;

}

In front end

$tb = tabledetails() ;
echo $tb[0];

What I have missed in this. Thanks in advance