在数据透视表中附加数据时，时间戳不会更新

If you want your pivot table to have automatically maintained created_at and updated_at timestamps, use the withTimestamps() method on the relationship definition.

return $this->belongsToMany('Role')->withTimestamps();

• For Laravel 4.2: Working With Pivot Tables
• Laravel 5.0: Working With Pivot Tables
• Laravel 5.1: Retrieving Intermediate Table Columns
• Laravel 5.2: Filtering Relationships Via Intermediate Table Columns
• Laravel 5.3: Filtering Relationships Via Intermediate Table Columns
• Laravel 5.4: Retrieving Intermediate Table Columns
• Laravel 5.5: Retrieving Intermediate Table Columns
• Laravel 5.6: Retrieving Intermediate Table Columns
• Laravel 5.7: Retrieving Intermediate Table Columns
• Laravel 5.8: Retrieving Intermediate Table Columns