Saving a Base64 string to disk as a binary using PHP

If you have a lot of data to write out that needs to be decoded before writing I would suggest using stream filters so decode the data as you write it...

$fh = fopen('where_you_are_writing', 'wb');
stream_filter_append($fh, 'convert.base64-decode');

// Do a lot of writing here. It will be automatically decoded from base64.

fclose($h);

I tried the below but did not work for me, was generating an empty image file.

file_put_contents('img.png', base64_decode($base64string));

this is how it worked for me:

$data = 'data:image/png;base64,AAAFBfj42Pj4';

list($type, $data) = explode(';', $data);
list(, $data)      = explode(',', $data);
$data = base64_decode($data);

file_put_contents('/tmp/image.png', $data);

I took the code from : How to save a PNG image server-side, from a base64 data string

function base64_decode_file($data)
{
    if(preg_match('/^data\:([a-zA-Z]+\/[a-zA-Z]+);base64\,([a-zA-Z0-9\+\/]+\=*)$/', $data, $matches)) {
        return [
                'mime' => $matches[1],
                'data' => base64_decode($matches[2]),
        ];
    }
    return false;
}

While reinventing the wheel has some entertainment and educational value, I would try to resist the temptation: Mailparse, Mail_mimeDecode

I had a similar situation, and this is what I did. As noted earlier, make sure to remove the extraneous lines before and after the base64 string.

<?php
$INPUT = "inputfile_base64_encoded.txt";
$OUTPUT = "output_decoded.zip";
$contents = file_get_contents($INPUT);
$bin = base64_decode($contents);
file_put_contents($OUTPUT, $bin);
?>

Chop off first and last line, base64decode and save under given filename.

done.

For big base64 strings from a DB you need use load()

$imgdata = $FromDB['BASE64']->load();
$imgdata =  base64_decode($imgdata);
file_put_contents($fileName, $imgdata);