function GetWebTheme($web)
{
	[string]$thmxURL = 
				[Microsoft.SharePoint.Utilities.ThmxTheme]::GetThemeUrlForWeb($web);
	[Microsoft.SharePoint.Utilities.ThmxTheme] $mytheme = 
				[Microsoft.SharePoint.Utilities.ThmxTheme]::Open($web.Site, $thmxURL);	
	Write-Host ""
	Write-Host "Current SPWeb URL:", $web.URL
	Write-Host "Current Theme:", $mytheme.Name, "[", $thmxURL, "]";
	Write-Host ""
}

function SetWebTheme($web, $themeName)
{
	[string]$themeUrl = “/sites/ASP-PHP/_catalogs/theme/” + $themeName + “.thmx”
	[Microsoft.SharePoint.Utilities.ThmxTheme]::SetThemeUrlForWeb($web, $themeUrl)
	$web.Update()

	Write-Host " -------------------------------------------- "
	Write-Host ""
	Write-Host "Current SPWeb URL:", $web.URL
	Write-Host "New Theme to apply:",  $themeName, "[", $themeUrl, "]";
	Write-Host ""
	Write-Host " -------------------------------------------- "
}

[string]$MyWebURL = "http://ch0015271v/sites/ASP-PHP/";
[string]$newWebTheme = "ASP-PHP"
$myweb = Get-SPWeb $MyWebURL;

cls
GetWebTheme $myweb
SetWebTheme $myweb $newWebTheme