Cannot update Created By (Author) field through powershell

Question

I'm trying to use powershell to add a new item to a SharePoint list AND set the created by/author field. I don't have much experience with powershell but this seems fairly straightforward.

I have a 2013 environment and a list called Favorites that users populate with links they want to save. However, I'd like to be able to add a favorite for a user as read and edit access is limited to items created by the user.

My powershell script:

Add-PSSnapin Microsoft.SharePoint.PowerShell -EA SilentlyContinue
$SPWeb = Get-SPWeb "http://sharepoint";
$SPList = $SPWeb.GetList("http://sharepoint/Lists/Favorites");
$userName = "i:0#.w|[domain]\[username]";
$user = Get-SPUser -web $SPWeb -Identity $userName;

$SPListItem = $SPList.Items.Add();
$SPListItem["URL"] = "http://www.cnn.com";
$SPListItem["Author"] = $user;
$SPListItem.Update();

However, this gives the error:

Exception calling "Update" with "0" argument(s): "Invalid data has been used to update    
the list item. The field you are trying 
to update may be read only."
At line:11 char:1
$SPListItem.Update();
~~~~~~~~~~~~~~~~~~~~
CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
FullyQualifiedErrorId : SPException

If the field has a read only property, I thought it would be possible to change that:

$SPList.Fields["Author"].ReadOnlyField = $false;

However, that gives me this error:

Property 'ReadOnlyField' cannot be found on this object; make sure it exists and is
settable.
At line:6 char:1
$SPList.Fields["Author"].ReadOnlyField = $false;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CategoryInfo          : InvalidOperation: (:) [], RuntimeException
FullyQualifiedErrorId : PropertyNotFound

Edit: after further investigation, there were recent security updates made to our SharePoint server by our network admin that may be related to this script no longer working. I will try to update this post with what I find out.

Any ideas are still appreciated.

Edit 2: see below for the solution I used.

Answer 1

Below is what I needed to change to get this to work:

Add-PSSnapin Microsoft.SharePoint.PowerShell -EA SilentlyContinue
$SPWeb = Get-SPWeb "http://sharepoint";
$SPList = $SPWeb.GetList("http://sharepoint/Lists/Favorites");
$userName = "i:0#.w|[domain]\[username]";
$user = Get-SPUser -web $SPWeb -Identity $userName;
$userString = "{0};#{1}" -f $user.ID, $user.UserLogin.Tostring()

$SPListItem = $SPList.Items.Add();
$SPListItem["URL"] = "http://www.cnn.com";
$SPListItem["Author"] = $userString;
$SPListItem.UpdateOverwriteVersion();

$userString is the correct format for the user and using UpdateOverweiteVersion() instead of update() saved the changes to the Author field.

Answer 2

Please, refer to this link to modify this field:

$SPSite = New-Object Microsoft.SharePoint.SPSite("http://sharepoint")
$SPWeb = $SPSite.OpenWeb()
$SPFieldUserValue = New-Object Microsoft.SharePoint.SPFieldUserValue($SPWeb,8, "#Test R.Test") 
$ListItem["Author"] = $SPFieldUserValue                   
$ListItem.Update() 
$SPWeb.Update()

As you can see, you must create a SPFieldUserValue as mentionned above. The number '8' is the user ID (you get it from Get-SPUser I guess -cannot test it right now-, or please check SPWeb users -$SPWeb.users ?-).

Other point, please check the $SPWeb.AllowUnsafeUpdates value. Must be to trueotherwise you won't be able to modify the ReadOnly property. According to https://sharepoint.stackexchange.com/a/100557/17814

Answer 3

Try adding an update right after creating the record....

$SPListItem = $SPList.Items.Add();
$SPListItem.Update();
$SPListItem["URL"] = "http://www.cnn.com";
$SPListItem["Author"] = $user;
$SPListItem.Update();