How to verify the image format when saving remote images using PHP?

How to verify the image format when saving remote images using PHP?

During development, sometimes we need to save images on the remote server locally, such as saving images uploaded by users or grabbing images from web pages. In order to ensure that the saved image format is correct, we need to verify the format of the remote image. This article will introduce how to implement remote image format verification in PHP and provide corresponding code examples.

1. Obtain the format of the remote image

To verify the format of the remote image, you first need to obtain the file extension of the remote image. You can use PHP's getimagesize() function to obtain remote image information, including the image's width, height, MIME type, etc. After obtaining the MIME type, we can extract the file extension from it.

The following is a sample code for getting the file extension of a remote image:

function getRemoteImageExtension($imageUrl){
    $imageInfo = getimagesize($imageUrl);
    $mime = $imageInfo['mime'];
  
    $extensions = [
        'image/jpeg' => 'jpg',
        'image/png' => 'png',
        'image/gif' => 'gif',
        // 其它图片格式
    ];
  
    $extension = $extensions[$mime] ?? '';
  
    return $extension;
}

// 调用示例
$imageUrl = 'https://example.com/image.jpg';
$extension = getRemoteImageExtension($imageUrl);
echo $extension;  // 输出：jpg

In the sample code, the getimagesize() function is used to get the remote image information, and then define the extensions of different types of pictures through arrays, and finally obtain the required extensions from them.

2. Verify the format of the remote image

After obtaining the file extension of the remote image, you can verify it. You can compare the obtained extension with the allowed image formats to determine whether the remote image meets the requirements.

The following is a sample code for verifying the format of remote images:

function validateRemoteImage($imageUrl){
    $extension = getRemoteImageExtension($imageUrl);
  
    $allowedExtensions = ['jpg', 'png', 'gif'];
  
    if(in_array($extension, $allowedExtensions)){
        return true;
    } else {
        return false;
    }
}

// 调用示例
$imageUrl = 'https://example.com/image.jpg';
if(validateRemoteImage($imageUrl)){
    echo '远程图片格式正确';
} else {
    echo '远程图片格式不正确';
}

In the sample code, the in_array() function is used to determine the obtained Whether the extension is in the array of allowed extensions. If it is among them, return true, indicating that the remote image format is correct; otherwise, return false, indicating that the remote image format is incorrect.

Through the above code examples, we can implement remote image format verification in PHP. When saving a remote image, first obtain the file extension of the remote image, and then determine whether it meets the requirements. This can largely avoid saving remote images in the wrong format.

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