Removeing duplicates inside for/foreach loop.

["Niccolo Machiavelli" <php.coder@xxxxxxxxx>]

$array = array(

  1 => array("order_number" => "10DA0DDEDAF97DB", "order_payment_first_name"
=>  "Mike", "order_payment_last_name" =>  "Smith"),

  2 => array("order_number" => "10DA0DDEDAF97DB", "order_payment_first_name"
=>  "Mike", "order_payment_last_name" =>  "Smith"),

  3 => array("order_number" => "45Y3453245T23T5", "order_payment_first_name"
=>  "Steve", "order_payment_last_name" =>  "Jobs"),

  4 => array("order_number" => "34RTB345T45T456", "order_payment_first_name"
=>  "Frank", "order_payment_last_name" =>  "Capra"),

  5 => array("order_number" => "567U457645645Y6", "order_payment_first_name"
=>  "John", "order_payment_last_name" =>  "Doe"),

  6 => array("order_number" => "7698234T456M963", "order_payment_first_name"
=>  "Bill", "order_payment_last_name" =>  "Williams"));

 

echo('<pre>');

print_r($array);

echo('</pre>');

 

My question is I want to remove duplicate order numbers in other words ditch
*one* of the Mike Smith rows there's a duplicate order number there. 

And I need to do it in either a for/foreach loop. Somehow there's got to be
a simple way to check and only output non duplicate order numbers while I'm
looping thru the data. Any help would be greatly appreciated. 

 

 

Thanks

php.code@xxxxxxxxx