Problem with parameter count in strstr()

Hi, I am trying to ensure that all data added to each element of $my_data_array has no commas, however I get an error message saying Warning: Wrong parameter count for strstr() $my_data_array[] = strstr( $data[1], ",", " " ); strstr( $data[2], ",", " " ).', '. strstr( $data[3], ",", " " ).', '. strstr( $data[6], ",", " " ).', '. strstr( $data[13], ",", " " ).', '. strstr( $data[14], ",", " " ).', '. strstr( $data[15], ",", " " ).', '. strstr( $data[16], ",", " " ).', '. strstr( $data[17], ",", " " ).', '. strstr( $data[18], ",", " " ).', '. strstr( $data[19], ",", " " ).', '. Could someone tell me what I am doing wrong here please? Thank you