$conditions = array();

foreach($GET as $k => $v) { if(preg_match("/(.*)()(.*)/",$k) { $c = explode("_",$k); $conditions[] = array( 'field' => $c[0], 'condition' => $c[1], 'val' => $v );
}else{ $conditions[] = array( 'field' => $k, 'condition' => "equalTo", 'val' => $v );
} }

It seems like you are giving your API user too much information about the internals, but if you really want to follow this path, I suggest you don't fight HTTP and use HTTP-friendly URLs. This gives your API users the ability to use URL-building libraries the way they were designed.

I suggest your API accept queries such as:

// foo > 1
"/WaferSearch?clauses[]=foo%20>%201"

// foo > 1 AND foo < 10
"/WaferSearch?clauses[]=foo%20>%201&clauses[]=foo%20<%2010"

// bar LIKE '%abcde%'
"/WaferSearch?clauses[]=bar+LIKE+%27%25abcde%25%27"

My suggested code is below. I replaced your "Wafer" model with my "Account" model. You will want to adjust the Model and the $valid_fields to suit your needs. Also, you will probably want more flexible operators ("LIKE", "IN", etc).

function is_valid_value($field_name, $field_value) {
    return TRUE;
}

Route::any('WaferSearch', function () {
    $valid_operators = array('=', '>', '>=', '<', '<=');
    $valid_fields    = array('id', 'username', 'email');
    // Output format to be compatible with YUI's default JSON structure for resultsets:
    // http://yuilibrary.com/yui/docs/autocomplete/#locating-results
    $response_obj    = (object) array(
        'status' => 'error',
        'query' => NULL,
        'data' => NULL,
    );
    $search_query = Account::query();
    $input_clauses = Input::get('clauses');
    $sql_where_parts = array();
    if(!isset($input_clauses) || !is_array($input_clauses)) {
        // handle case with invalid input
        $error_message = 'no valid clauses found (param "clauses" must be an array)';
        Log::error($error_message);
        $reponse_obj->message = $error_message;
    } else {
        $valid_clauses = 0;
        foreach($input_clauses as $this_clause) {
            $preg_pattern = '/^(' . implode('|', array_map('preg_quote', $valid_fields)) . ')\s*(' . implode('|', array_map('preg_quote', $valid_operators)) . ')\s*(.*)$/';
            if(preg_match($preg_pattern, $this_clause, $matches)) {
                $fieldname = $matches[1];
                $operator  = $matches[2];
                $new_value = $matches[3];
                // do some $new_value validation based on $fieldname
                if(!is_valid_value($fieldname, $new_value)) {
                    Log::error('Bad field value.');
                    continue;
                }
                $search_query->where($fieldname, $operator, $new_value);
                $sql_where_parts[]= implode(' ', array($fieldname, $operator, $new_value));
                $valid_clauses++;
            } else {
                // handle case with no input
                Log::error('invalid clause found (does not match expected format)');
                continue;
            }
        }
        if(0 < $valid_clauses) {
            $matchingWafers = $search_query->get();
            $response_obj->status = 'okay';
            $response_obj->query = implode(' AND ', $sql_where_parts);
            $response_obj->data = (object) array(
                'resultCount' => $matchingWafers->count(),
                'results' => (array) $matchingWafers,
            );

        } else {
            $error_message = 'No valid clauses to process';
        }
    }

    return Response::json($response_obj);
});