Using php to download network images does not display

With the continuous development of the Internet era, pictures have become an indispensable element in modern life. In website development, we often need to use PHP to download images from the Internet and display them on the page. However, sometimes when using PHP to download network images, you may encounter situations where the images cannot be displayed. This article will discuss and solve this problem.

1. Methods of downloading network images

PHP provides a variety of ways to download network images. Here are two of the methods:

1. Use the curl function to download images.

curl is a powerful open source library that supports multiple protocols and can complete various network operations, including downloading files. The code for using the curl function to download images is as follows:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
$data = curl_exec($ch);
curl_close($ch);

Among them, $url represents the link address of the image to be downloaded. Use the curl_setopt function to set parameters, the commonly used ones are:

• CURLOPT_RETURNTRANSFER: Set to 1 to save the returned result to the $data variable.
• CURLOPT_HEADER: Set to 0 to indicate no header information is returned.
• CURLOPT_FOLLOWLOCATION: Set to 1 to support redirection.

This code will save the file contents to the $data variable. If you want to save the file locally, you can use the file_put_contents function:

file_put_contents($path, $data);

where $path represents the path to save the file.

2. Use the file_get_contents function to download images

In addition to using the curl function, you can also use the PHP built-in function file_get_contents to download images. Compared with the curl function, the file_get_contents function is simpler to use.

$data = file_get_contents($url);

This code will read the contents of the specified URL into the $data variable. If you want to save to a local file, you can use the file_put_contents function, which is the same as using the curl function.

2. Reasons and solutions for why images cannot be displayed

When you use PHP to download network images and display them on the page, you may find that the images cannot be displayed normally. Here is a summary of the possible reasons and solutions for this situation.

1. Incomplete picture download

Sometimes the downloaded picture may not be downloaded completely due to network reasons, resulting in the failure to display properly. You can determine whether the download is completed by comparing the local file size and the actual file size. The following is a code example:

$data = curl_exec($ch); // 使用 curl 函数下载文件
$content_length = curl_getinfo($ch, CURLINFO_CONTENT_LENGTH_DOWNLOAD); // 获取文件大小
curl_close($ch);

if(strlen($data) != $content_length){ // 判断文件大小与下载大小是否一致
    exit("下载的文件不完整！");
}

2. The image format is incorrect

Sometimes, the downloaded network image may not be The correct image format will not be displayed properly at this time. You can use PHP's built-in getimagesize function to determine whether the image is correct.

if(@!getimagesize($path)){ // 判断图片是否正确
    unlink($path); // 删除下载的图片
    exit("下载的不是图片文件！");
}

3. The image path is incorrect

When the image path is incorrect, the image will not be displayed normally. At this time, you need to check whether the image path is correct, including file name, file path, etc.

4. Browser cache problem

Sometimes, even if the image has been downloaded and saved locally, the browser still cannot display the image normally. This may be a browser cache problem. You can try clearing your browser cache or adding random parameters after the image link to avoid caching issues.

<img src="http://example.com/image.jpg?<?php echo time(); ?>" alt="image">

The above is about the solution to the problem that network images cannot be displayed after downloading them using PHP. I hope it can be helpful to everyone.

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