Error when converting base64 to image file in PHP - php

Question

I get an error when I convert base64 to an image file, it creates an image file but when I open it, it is an error image file?
In the image error message: Looks like we don't support this file format
My code is as follows
public function Base64ToImg($str,$ouput){
$bs64 = (strpos($str, ",")) ? explode(',',$str)[1] : $str;
$bin = base64_decode($bs64);
$size = getImageSizeFromString($bin);
$ext = substr($size['mime'], 6);
$ouput = $ouput.".$ext";
file_put_contents($ouput,$bin);
return $ouput;
}
UPDATE
The error is not in my code but because I am sending base64 code the image via POST method but in my base64 code contains + character so when sending via POST it will be removed + character goes error, I used js code logo = logo.replaceAll("+","*"); to convert character + to * and PHP code $logo = str_replace("*", "+", $logo); to convert * back to +, and it worked fine for me