How to Properly Convert Base64 Image Strings to JPEG Files in PHP?

Converting Base64 Strings to Image Files in PHP

The issue arises when converting base64 image strings to image files. The base64 string often contains additional metadata such as "data:image/png;base64," which interferes with proper decoding.

Understanding the Problem

The default base64 decoding function expects pure image data, but the extra metadata present in the base64 string corrupts the decoding process. This results in an invalid image when attempted to be displayed or saved.

Solution: Removing Metadata Before Decoding

To resolve this issue, modify the conversion function to split the string on commas and extract the actual image data. The modified function below efficiently handles this situation:

function base64_to_jpeg($base64_string, $output_file) {
    // Open the output file for writing
    $ifp = fopen($output_file, 'wb');

    // Split the string on commas
    // $data[0] == "data:image/png;base64"
    // $data[1] == <actual base64 string>
    $data = explode(',', $base64_string);

    // Validate that the string is in the correct format
    if (count($data) < 2) {
        throw new InvalidArgumentException("Invalid base64 string");
    }

    // Extract and decode the actual image data
    fwrite($ifp, base64_decode($data[1]));

    // Clean up the file resource
    fclose($ifp);

    return $output_file;
}

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