Adds a module-specific search option to a search expression.
Search options are added using search_expression_insert(), and retrieved using search_expression_extract(). They take the form option:value, and are added to the ordinary keywords in the search expression.
$expression: The search expression to add to.
$option: The name of the option to add to the search expression.
$value: The value to add for the option. If present, it will replace any previous value added for the option. Cannot contain any spaces or | characters, as these are used as delimiters. If you want to add a blank value $option: to the search expression, pass in an empty string or a string that is composed of only spaces. To clear a previously-stored option without adding a replacement, pass in NULL for $value or omit.
The search expression, with any previous value for this option removed, and a new $option:$value pair added if $value was provided.
function search_expression_insert($expression, $option, $value = NULL) {
$expression = new SearchExpression($expression);
return $expression
->insert($option, $value)
->getExpression();
}