Hey Adam try this, it worked for me:
PROCEDURE ISU_TEST_4 (Customer_Email IN varchar2, Cust_ID_Out OUT number, ERROR OUT number) IS
BEGIN
SELECT Customer_ID
INTO Cust_ID_Out
FROM Isu_Customer
WHERE Email = Customer_Email AND ROWNUM=1;
ERROR := 0;
EXCEPTION
when others then
ERROR := 1;
END;
$cn_cur = ocilogon($a, $b, $c);
$sEmail = "chuck_pencils@test.com";
$s_sp = "begin ISU_TEST_4 ('$sEmail',:Cust_ID_Out, :ERROR); end;";
$a_Sql_Parse = ociparse($cn_cur,$s_sp);
OCIBindByName($a_Sql_Parse, ":Cust_ID_Out", &$lCust_ID);
OCIBindByName($a_Sql_Parse, ":ERROR", &$lError);
ociExecute($a_Sql_Parse);
print $lCust_ID;
print $lError;
ocifreestatement($a_Sql_Parse);
ocilogoff($cn_cur);