Php / Laravel check for duplicate in loop - php

Question

I am trying to check whether a generated string is in my database table or not.
If there is no duplicate I want to return and save it.
If there is a duplicate I want to generate a new string and save it
currently this function does not return me the generated token:
public function checkForHashDuplicate($string)
{
$newToken = '';
$inquiries = DB::table('inquiries')->get();
foreach($inquiries as $inquiryKey => $inquiryValue)
{
while($inquiryValue->android_device_token == $string)
{
$newToken = generateAlphanumericString();
if($newToken != $inquiryValue->android_device_token)
{
return $newToken;
}
}
}
}
$inquiry->android_device_token = $this->checkForHashDuplicate($hash);

Answer 1

A simplified version of your code is:
public function checkForHashDuplicate($string)
{
do {
// generate token
$newToken = generateAlphanumericString();
// find token in a DB
$duplicate = DB::table('inquiries')
->where('android_device_token', '=', $newToken)->first();
// if token is FOUND `$duplicate` has truthy value
// and `do-while` keeps running
// else `$duplicate` is falsy and `do-while` breaks
} while ($duplicate);
return $newToken;
}

Answer 2

Instead of using:
$inquiries = DB::table('inquiries')->get();
and loop, use where like:
$inquiries = DB::table('inquiries')->where('android_device_token', '=', $string)->get();
if( count($inquiries ) == 1 )
{
// found
}
else
{
// Not found, generate new one
}

Answer 3

You can check like this:
public function checkDuplicate($string){
$count = DB::table('inquiries')->where('android_device_token',$string)->count();
if($count==0){
// $string exists
return generateAlphanumericString();
}else{
// $string doesn't exists
return $string;
}
}
Now, use this function to assign value of $string or new token as
$inquiry->android_device_token = $this->checkForHashDuplicate($hash);
Hope you understand.