How to replace contents of fields in Drupal 7?

Prepare a menu item for selecting the field name, providing the search text & replace text.
/**
 * Implements hook_menu().
 */
 function custom_menu() {
    $items = array();
/* To replace content like URL's in body fields */
    $items['admin/config/development/replace-content'] = array(
        'title' => 'Replace Content',
        'description' => t("To replace contents like URL's in Body field when Database deployed from different environment"),
        'page callback' => 'drupal_get_form',
        'page arguments' => array('replace_content'),
        'access arguments' => array('replace content'),
    );
return $items;
}
/**
 * Configuration form for Replacing Contents in the Database based on the selected fields
 */
function replace_content($form, &$form_state){
  global $base_url;
    $fieldsList = field_info_field_map();
    $field_arr = array();
    if(is_array($fieldsList) && count($fieldsList)){
        foreach($fieldsList as $fieldName => $fieldDetails){
            $field_arr[$fieldName] = $fieldName;
        }
    }
    $form['search_parameter'] = array(
            '#type' => 'textfield',
            '#title' => t('Enter text to search in body field'),
            '#default_value' => 'http://www.google.com',
            '#required' => TRUE
    );
    $form['replace_parameter'] = array(
            '#type' => 'textfield',
            '#title' => t('Enter text to replace in body field'),
            '#default_value' => $base_url,
            '#required' => TRUE
    );
    $form['search_in_fields'] = array(
            '#type' => 'select',
            '#title' => 'Fields',
            '#options' => $field_arr,
            '#description' => t('Select the fields in which the content has to get replace'),
            '#multiple' => TRUE,
            '#required' => TRUE
    );
    $form['submit'] = array( '#type' => 'submit', '#value' => t('Replace'));
    return $form;
}
/* Replace content submit function */
function replace_content_submit($form, &$form_state){
    $values = $form_state['values'];
    $search_parameter = $values['search_parameter'];
    $replace_parameter = $values['replace_parameter'];
    $search_in_fields = $values['search_in_fields'];
    $affected_rows_exists = FALSE;
    foreach($search_in_fields as $selected_field){
            $table_name = 'field_data_' . $selected_field;
            $revision_table_name = 'field_revision_' . $selected_field;
            $field_name = $selected_field . '_value';
            if(db_table_exists($table_name)){
                    $affected_rows = db_update($table_name)
  ->expression($field_name, "replace($field_name, :search, :replace)", array(':search' => $search_parameter, ':replace' => $replace_parameter))
    ->execute();
                    if($affected_rows){
                            $affected_rows_exists = TRUE;
                            $row_text = (count($affected_rows)>1) ? 'rows' : 'row';
                            drupal_set_message(t($affected_rows . ' ' . $row_text .  ' got affected in ' . $table_name . '.'));
                    }
                    $affected_revision_rows = db_update($revision_table_name)
  ->expression($field_name, "replace($field_name, :search, :replace)", array(':search' => $search_parameter, ':replace' => $replace_parameter))
    ->execute();
                    if($affected_revision_rows){
                            $affected_rows_exists = TRUE;
                            $row_text = (count($affected_revision_rows)>1) ? 'rows' : 'row';
                            drupal_set_message(t($affected_revision_rows . ' ' . $row_text . ' got affected in ' . $revision_table_name . '.'));
                    }
            }else{
            exit;
            }
    }
    if(!$affected_rows_exists){
            drupal_set_message(t('None of the rows got affected.'));
    }
}