cadenas de caracteres

[Hidek1]

ahi tienes .. usando preg_replace es facil ..

Código PHP:

<?php
$string = "OXXXXXXXXXXXXXXOOOOOOOOOOOOOXXXXXXXXXXOOOO";
$string = preg_replace('/(X+)/','<span style="color:red">$1</span>', $string);
$string = preg_replace('/(O+)/','<span style="color:green">$1</span>', $string);
echo $string;
?>
 

saludos!