function createTableFromJson(array $json){
    $result = "";
    
    if(isset($json["tables"])){
        foreach($json["tables"] as $tableName => $data){
            $result .= "CREATE TABLE `".$tableName."`";
            
            if(isset($data["columns"]) && count($data["columns"]) >= 1){
                $result .= " (";
                $columnDefinations = [];
                foreach($data["columns"] as $columnName => $columnDefination){
                    $columnDefinations[] = "`".$columnName."` ".$columnDefination."";
                }
                
                $result .= implode(", ", $columnDefinations);
                
                if(isset($data["mods"])){
                    $result .= ", ".implode(", ", $data["mods"]);
                }
                
                $result .= ")";
            }
            
            $result .= ";".PHP_EOL;
        }
    }
    
    return $result;
}

echo createTableFromJson(json_decode($твоя_строка_с_json));