For use PHPv5 functions in PHPv4 i use simple script:
<?php
$funcs=array(
        'oci_connect'=>'OCILogon',
        'oci_parse'=>'OCIParse',
        'oci_execute'=>'OCIExecute',
        'oci_fetch'=>'OCIFetch',
        'oci_num_fields'=>'OCINumCols',
        'oci_field_name'=>'OCIColumnName',
        'oci_result'=>'OCIResult',
        'oci_free_statement'=>'OCIFreeStatement',
);
foreach ($funcs as $k=>$v)
    {
        if (!function_exists($k))
            {
                $arg_string='$p0';
                for ($i=1;$i<20;$i++) {
                    $arg_string.=',$p'.$i;
                }
                eval ('function '.$k.' () {
                        list('.$arg_string.')=func_get_args();
                        return '.$v.'('.$arg_string.');
                        }
                ');
            }
    }
?>
simple, but it work. :-)