如何让WordPress媒体库识别.pdf文件

function modify_post_mime_types( $post_mime_types ) { 
// 选择mime类型，这里用: 'application/pdf' 
// 然后扩充数组，定义label的文字 
$post_mime_types['application/pdf'] = array( __( 'PDFs' ), __( 'Manage PDFs' ), 
_n_noop( 'PDF <span class="count">(%s)</span>', 'PDFs <span class="count">(%s)</span>' ) ); 
// then we return the $post_mime_types variable 
return $post_mime_types; 
} 
// Add Filter Hook 
add_filter( 'post_mime_types', 'modify_post_mime_types' );

function get_allowed_mime_types()

'jpg|jpeg|jpe' => 'image/jpeg', 
'gif' => 'image/gif', 
'png' => 'image/png', 
'bmp' => 'image/bmp', 
'tif|tiff' => 'image/tiff', 
'ico' => 'image/x-icon', 
'asf|asx|wax|wmv|wmx' => 'video/asf', 
'avi' => 'video/avi', 
'divx' => 'video/divx', 
'flv' => 'video/x-flv', 
...

$post_mime_types['application/pdf'] = array( __( 'PDFs' ), __( 'Manage PDFs' ), 
_n_noop( 'PDF <span class="count">(%s)</span>', 'PDFs <span class="count">(%s)</span>' ) );