SqlPdo

<?php

$database = "nome_do_seu_banco";
$username = "root";
$password = "";

try {
    $con = new PDO("oci:dbname={$database}", $username, $password);
}

catch(PDOException $exception){
    echo "Connection error: " . $exception->getMessage();
}



$job = isset( $_GET['job'] ) ? $_GET['job'] : null;

$id  = isset( $_GET['id'] ) && is_numeric( $_GET['id'] ) ?  $_GET['id'] : null;

 $sql = $con->prepare("SELECT CO21CODCOT FROM CO21T1 WHERE CO21CODCOT  ='{$id}'");
 $sql->execute();

 if( $sql->rowCount() >= 1 ){

    while( $rows->$sql->fetch( PDO::FETCH_ASSOC ) )
    {
        //....
    }

 }else{

  // O que deseja fazer se não encontrar
}


 ?>