Use this code as an example:
replace scott with your user name
replace tige with your password
replace orcl with SID was given in the setup email.
<?php
if ($conn=OCILogon("scott", "tiger", "orcl")) {
echo "Successfully connected to Oracle using OCI extension.n";
OCILogoff($conn);
} else {
$err = OCIError();
echo "Error in connecting to the Oracle." . $err[text];
}
?>