Custom form validation rule

Im going to use something like table.column:existing_value instead of  table.column|existing_value, that should work.

Quick regex question. Anyone know how to use preg_match to match for both of those? And just check if the third matched value is there? Im having trouble with it, im not a Regex ninja..

PHP Code:

<?php
$s = [
    'table.column',
    'table.column:value'
    ];

//$pattern = '/^(\S+)\.(\S+)\:(\S+)?$/';
$pattern = '/^(\S+)\.(\S+)$/';

foreach($s as $str){
    if(preg_match($pattern, $str, $matches))
    {
        echo "Successfuly matched string: {$str}\n";
        print_r($matches);
    }
    else
    {
        echo "No matches for string: {$str}\n";
    }
    echo "==============\n";
} 


Result:

Successfuly matched string: table.column

Array
(
    [0] => table.column
    [1] => table
    [2] => column
)
==============
Successfuly matched string: table.column:value
Array
(
    [0] => table.column:value
    [1] => table
    [2] => column:value
)
==============

What im looking for is:

Successfuly matched string: table.column
Array
(
   [0] => table.column
   [1] => table
   [2] => column
)
==============
Successfuly matched string: table.column:value
Array
(
   [0] => table.column:value
   [1] => table
   [2] => column
   [2] => value
)
==============

I know I can use the question mark to match for the last string or not, but im having issues including the : in that condition..

What I have now works, its just too complicated when REGEX can get rid of some code..

PHP Code:

<?php defined('BASEPATH') OR exit('No direct script access allowed');

class MY_Form_validation extends CI_Form_validation {

    public function is_unique($str, $field)
    {
        // No : found, use the default is_unique
        if(strpos($field, ':') === FALSE)
        {
            return parent::is_unique($str, $field);
        }

        // If we can match for a table.column:value, assume were editing
        if( preg_match('/^(\S+)\.(\S+)\:(\S+)?$/', $field, $matches) !== FALSE )
        {
            $table = $matches[1];
            $field = $matches[2];
            $ignore = $matches[3];

            $this->CI->db
                ->select('*')
                ->from($table)
                ->where($field, $str);

            if( ! is_null($ignore))
                $this->CI->db->where_not($field, $ignore);

            return $this->CI->db->num_rows() === 0;
        }

        // If : was found but regex not matched..
        Logger_lib::error("Failed to match 'table.column' as well as 'table.column:value' for is_unique form validation check", TRUE);
        return FALSE;
    }
} 


Thanks