<?

//find string from big string then use search and replace to get rid of spaces in favour of underscores

///////////////////////////////////////////////////////////////////////////////////////////
//you can delete this line and replace it with something like $string1 = $_POST['string'];
or whatever it may //be called And all variable names can be changed just remember
to change them all the way through!
///////////////////////////////////////////////////////////////////////////////////////////
$string1 = $_GET['string'];

//first bracket
$bracket_1 = strpos($string1, "[");

//second bracket
$bracket_2 = $bracket_1 + 2;

//find first closing bracket to identify the little string to replace spaces within.
$c_bracket = strpos($string1, "]", $bracket_2);

// get the number of characters between the brackets
$chars = $c_bracket - $bracket_2;


//now got the bracket's positions we can get this mini string between them
$sub = substr($string1, $bracket_2, $chars);

//now we can search and replace the spaces :)
$no_spaces = str_replace(" ", "_", $sub);

//final string with no spaces
echo $no_spaces;

//shadow-x :) Spread and use as needed!

?>

$string = preg_replace('#\[\[(.[^\]]*)\]\]#e', 'str_replace(" ","_","$1");', $string);