PHP警告：usort（）期望参数1为数组，在＆array_slice（）中给出null，期望参数1为数组，null为

Question

function prepare_items() {
  $columns  = $this->get_columns();
  $hidden   = array();
  $sortable = $this->get_sortable_columns();
  $this->_column_headers = array( $columns, $hidden, $sortable );
  usort( $this->$data, array( &$this, 'usort_reorder' ) );
  $per_page = 5;
  $current_page = $this->get_pagenum();
  $total_items = count( $this->data );
  $this->found_data = array_slice( $this->data,( ( $current_page-1 )* $per_page ), $per_page );
  $this->set_pagination_args( array(
    'total_items' => $total_items,
    'per_page'    => $per_page
  ) );
  $this->items = $this->found_data;}

i get thia error from code above.

Warning: usort() expects parameter 1 to be array, null given in [...]

Warning: array_slice() expects parameter 1 to be array, null given in [...]

can anyone help me to solve his problems?

Answer 1

i think $this->$data returns empty. Make sure $this->$data returns array and check the value (if(!empty($this->$data)) and proceed with function

function prepare_items() {
  $columns  = $this->get_columns();
  $hidden   = array();
  $sortable = $this->get_sortable_columns();
  $this->_column_headers = array( $columns, $hidden, $sortable );
if(!empty($this->$data) {
  usort( $this->$data, array( &$this, 'usort_reorder' ) );
  $per_page = 5;
  $current_page = $this->get_pagenum();
  $total_items = count( $this->data );
  $this->found_data = array_slice( $this->data,( ( $current_page-1 )* $per_page ), $per_page );
  $this->set_pagination_args( array(
    'total_items' => $total_items,
    'per_page'    => $per_page
  ) );
  $this->items = $this->found_data;}}