$perms = array('lectura', 'escritura', 'borrado');
$roles = array('admin', 'anonimo', 'logado');
$roles_perm = array('admin' => array('lectura', 'escritura','borrado'), user => array('lectura'));
$user = array('name' => 'pepito', 'roles' => array('logado','admin'));

global $user,$roles_perm;

function control_access($perm = FALSE) {
  global $user,$roles_perm;
  $roles = $user['roles'];
  foreach ($roles as $key => $value) {
    $perms = $roles_perm($value);
    if (in_array($perm,$perms)) {
       return TRUE;
    }
  }
  return FALSE;
}

...

if (control_access('escritura')) {

....

}

<?php
$pattern[] ='/\[red\](.*)\[\/red\]/i';
$pattern[] = '/\[blue\](.*)\[\/blue\]/i';
$replace[] = '<font color="red">${1}</font>';
$replace[] = '<font color="blue">${1}</font>';
$text = "El [blue]perro[/blue] de san roque no [red]tiene[/red] rabo";
print preg_replace($pattern,$replace,$text);
?>