$string = PREG_SPLIT( '/\s/', $string, NULL, PREG_SPLIT_NO_EMPTY );
$string = IMPLODE( '+', $string );
// ...or:
$string = TRIM( $string );
$string = PREG_REPLACE( '/\s+/', '+', $string );
//...or:
PHP Code:
$string = PREG_REPLACE( '/\s+/', '+', $string );
$string = TRIM( $string, '+' )