#Specify tenant admin and site URL
$Username = "admin@contoso.onmicrosoft.com"
$Password = Read-Host -Prompt "Please enter your password" -AsSecureString
$Site = "https://contoso.sharepoint.com/sites/projects"
$Context = New-Object Microsoft.SharePoint.Client.ClientContext($Site)
$Creds = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Username,$Password)
$Context.Credentials = $Creds

#Search Subsite Templates
#$Templates = $Context.Site.GetWebTemplates("1043","0")
#$Context.Load($Templates)
#$Context.ExecuteQuery()
#$Templates | Where {$_.Name -like "*STS#0*" } | Select Name, Description

#Main / project

#Load CSV
$dataSource = import-csv “C:tempcontoso.csv”

foreach($dataRecord in $dataSource)
{
    #Define properties
$projectnummer = $dataRecord.Projectnummer
$project = $dataRecord.Project

#check if subsite is present or not
$web = $Context.Web
$Context.Load($web.Webs)
$Context.ExecuteQuery()

$subweb = $web.Webs | where{$_.Url -like "*$projectnummer*"}
if($subweb)
{
    #Execute if subsite exists
    Write-Host "Project $projectnummer exists" -ForegroundColor Green
    continue
}
else
{
    #Execute if subsite does not exists
    Write-Host "Project $projectnummer does not exists yet, creating..." -ForegroundColor Green

    #Create Subsite in root
    $Subsite = New-Object Microsoft.SharePoint.Client.WebCreationInformation
    $Subsite.WebTemplate = "STS#0"
    $Subsite.Title = "$project"
    $Subsite.Description = "$projectnummer"
    $Subsite.Url = $projectnummer
    $Subsite.Language = "1043"
    $SubWeb = $Context.Web.Webs.Add($Subsite)
    $Context.Load($SubWeb)
    $Context.ExecuteQuery()
}
}

function GetClientContext($url, $user, $password) {
 $context = New-Object Microsoft.SharePoint.Client.ClientContext($url)
 $credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($user, $password)
 $context.Credentials = $credentials
 return $context
}

#variables
#top level site
$WebUrl = "https://test.sharepoint.com"
#subsite name/url
$newWebURL = "subsite"
#subsite of subsite url
$SubSubsiteUrl = "subsite2"

#Create subsite
$context = GetClientContext $WebUrl $User $Pass
#create site here
$Subsite = New-Object Microsoft.SharePoint.Client.WebCreationInformation
$Subsite.WebTemplate = "STS#0"
$Subsite.Title = "$newWebURL"
$Subsite.Url = "$newWebURL"
$SubWeb = $context.Web.Webs.Add($Subsite)
$context.Load($SubWeb)
Try{
    $context.ExecuteQuery()
    LogWrite "Success creating site for $newWebURL"
}
Catch{
    LogWrite "Error creating subsite for $newWebURL $_.Exception.Message"
}

#Create subsite of subsite
$newWebFullURL = $WebUrl + "/" + $newWebURL
$context = GetClientContext $newWebFullURL $User $Pass
#create site here
$Subsite = New-Object Microsoft.SharePoint.Client.WebCreationInformation
$Subsite.WebTemplate = "STS#0"
$Subsite.Title = "$SubSubsiteUrl"
$Subsite.Url = "$SubSubsiteUrl"
$SubWeb = $context.Web.Webs.Add($Subsite)
$context.Load($SubWeb)
Try{
    $context.ExecuteQuery()
    LogWrite "Success creating site"
}
Catch{
    LogWrite "Error creating site $_.Exception.Message"
}