.' 2>&1'  was missing
.' 2>&1'  was missing

This is working for me now and I get the errors back.

```
 exec($this->the_command .' 2>&1' , $output, $return_var);
```

eg:

Parameter 'report_type_id' of type 'java.lang.Integer caused java.lang.NumberFormatException For input string: "ytreyytre"
cossou/JasperPHP,cossou/JasperPHP,cossou/JasperPHP