Replace a string in directory names, filenames and file content using Powershell

I used the script below to change the directory names, file names and file contents. I understand there might be easier ways to do this using the pipe | operator but this makes sense to me at the moment (I'm relatively new to Powershell).

# change these three variables to suit your requirements
$baseDirectory = "C:\Food\"
$a = "Avocado"
$b = "Burger"

# get all files
$files = Get-ChildItem $baseDirectory -File -Recurse
# get all the directories
$directorys = Get-ChildItem $baseDirectory -Directory -Recurse

# replace the contents of the files only if there is a match
foreach ($file in $files)
{
    $fileContent = Get-Content -Path $file.FullName

    if ($fileContent -match $a)
    {
        $newFileContent = $fileContent -replace $a, $b
        Set-Content -Path $file.FullName -Value $newFileContent
    }
}

# change the names of the files first then change the names of the directories

# iterate through the files and change their names
foreach ($file in $files)
{
    if ($file -match $a)
    {
        $newName = $file.Name -replace $a, $b
        Rename-Item -Path $file.FullName -NewName $newName
    }
}

# reverse the array of directories so we go deepest first
# this stops us renaming a parent directory then trying to rename a sub directory which will no longer exist
# e.g.
# we might have a directory structure "C:\Rename\Rename"
# the file array would be [ C:\Rename, C:\Rename\Rename ]
# without reversing we'd rename the first directory to "C:\NewName"
# the directory structure would now be "C:\NewName\Rename"
# we'd then try to rename C:\Rename\Rename which would fail
[array]::Reverse($directorys)

# iterate through the directories and change their names
foreach ($directory in $directorys)
{
    if ($directory -match $a)
    {
        $newName = $directory.Name -replace $a, $b
        Rename-Item -Path $directory.FullName -NewName $newName
    }
}

I wouldn't even try to edit potentially binary files,
so the following script processes only specified file types
and for security does a backup.

$baseDirectory = "C:\Food\"
$a = "Avocado"
$b = "Burger"
$Include = '*.sln','*.cs'


Pushd $baseDirectory

# process all file and  directory names 
Get-ChildItem -Filter "*$a*" -Recurse|
  Rename-Item -NewName {$_.Name -replace $a,$b} -confirm


Get-ChildItem -Include $Include -Recurse | ForEach-Object{
  if (Select-String -Path $_ -Pattern $a -quiet){
    $BakName = "{0}.bak" -f $_.FullName
    $OldName = $_.FullName
    $_ | Move-Item -Destination $BakName -force
    (Get-Content $BakName) -replace $a,$b | Set-Content $OldName
  }
}
PopD