These function dynamically generate an url string depending on the setted parameters.

I would love to hear suggestions on how to simplify all these nested conditions :

function _amu_hal_generate_url($  config) {    $  url = variable_get('amu_hal_url_ws') . 'search/';    if ($  config->retrieval_method_select == 'by_user_fields') {     if (arg(0) == 'user' && arg(2) == '') {       $  url .= '?';       $  user = user_load(arg(1));        if ($  user->field_selected_publis) {         $  url = substr($  url, 0, -1);         $  config->docids_publis = $  user->field_selected_publis["und"][0]["value"];         $  config->retrieval_method_select = 'by_docids';       }        elseif ($  user->field_identifiant_hal) {         $  url .= 'fq=authIdHal_i:' . $  user->field_identifiant_hal["und"][0]["value"] . '';       }        elseif ($  user->field_auth_hal) {         foreach ($  user->field_auth_hal["und"] as $  user_id) {           $  tabFormesAuteur[] = $  user_id["value"];         }         array_walk_recursive($  tabFormesAuteur, function (&$  value) {           $  value = ucwords(strtolower($  value));         });         $  authLastNameFirstName_s = '("';         $  authLastNameFirstName_s .= implode('" OR "', $  tabFormesAuteur);         $  authLastNameFirstName_s .= '")';         if ($  config->halId_s != '') {           $  url .= $  config->halId_s . '&fq=';         }         else {           ($  config->hal_struct_id != '') ? $  url .= 'fq=structId_i:' . $  config->hal_struct_id : $  url .= '';         }         $  url .= '&fq=authLastNameFirstName_s:' . urlencode($  authLastNameFirstName_s) . '';       }       else {         $  authLastNameFirstName_s = '("' . ucwords(strtolower($  user->name)) . '")';         if ($  config->halId_s != '') {           $  url .= $  config->halId_s . '?';         }         else {           ($  config->hal_struct_id != '') ? $  url .= '?fq=structId_i:' . $  config->hal_struct_id : $  url .= '';         }         $  url .= '&fq=authLastNameFirstName_s:' . urlencode($  authLastNameFirstName_s) . '';       }     }   }    if ($  config->retrieval_method_select == 'by_docids') {     // explode each lines     $  tabdocids = preg_split("/\r\n|\r|\n/", $  config->docids_publis);     $  end = end($  tabdocids);     $  docidValues = '(';     foreach ($  tabdocids as $  docid) {       if ($  end != $  docid) {         $  docidValues .= $  docid . ' OR ';       }       else {         $  docidValues .= $  docid . ')';       }     }     $  url .= '?fq=docid:' . urlencode($  docidValues);     $  url .= '&rows=2000';    }    if ($  config->retrieval_method_select == 'by_multi_hal_attributes') {     // soit par collection soit structure     if ($  config->halId_s != '') {       $  url .= $  config->halId_s . '?';     }     else {       ($  config->hal_struct_id != '') ? $  url .= '?fq=structId_i:' . $  config->hal_struct_id : $  url .= '';     }      if ($  config->docType_s != '') {       $  tabdocType_s = preg_split("/\r\n|\r|\n/", $  config->docType_s);       $  end = end($  tabdocType_s);       $  docType_sValues = '(';       foreach ($  tabdocType_s as $  doctype) {         if ($  end != $  doctype) {           $  docType_sValues .= $  doctype . ' OR ';         }         else {           $  docType_sValues .= $  doctype . ')';         }       }       $  url .= '&q=docType_s:' . urlencode($  docType_sValues);     }     $  url .= '&rows=' . $  config->hal_last_pub_rows;   }    if ($  config->retrieval_method_select == 'by_single_hal_id') {     $  url .= '?fq=halId_s:' . $  config->hal_id;   }   $  url .= '&fl=' . $  config->displayed_fields;    if ($  config->year) {     $  url .= '&fq=producedDateY_i:' . $  config->year;   }   $  url .= '&sort=producedDate_tdate+desc';    return $  url; }