file_get_contents创建一个空文件

Question

how can I prevent file_get_contents from creating an empty file when being used as a test condition in an if clause?

An empty file is created regardless, which causes a subsequent call in a different method to getimagesize() to fail.

The problem is, that as I have my code setup, the first time it is called will determine to save an image or to display a previously saved imaged. This is in part dependent on the presence of a file. As an empty file is created, this causes problems when calling my code subsequent times.

Is the easiest way to add a check if the file exists and is greater than 0?

Regardless of if my code works, file_get_contents will still output an error. This error is accounted for and dealt with(by my if condition), so I would like to avoid the error interrupting the output of my application if possible. Is there a way to turn this off without hiding actual errors?

if (file_put_contents($imageDir . $pk . '.jpg', file_get_contents($pic_url))) 
{
        return $imageDir . $pk . '.jpg'; 
} 
else 
{
        return 'removed.jpg';
}

Answer 1

It isn't file_get_contents() that is creating an empty file, it is file_put_contents().

file_put_contents() will create a file even if the second parameter is empty. Hence, empty file.

You'll need to check the file exists first.

The easiest fix would be to move file_put_contents() inside the conditional, so that it only creates a file if there are contents.

if (($filecontents = file_get_contents($pic_url)) !== false) 
{
    file_put_contents($imageDir . $pk . '.jpg', $filecontents);
    return $imageDir . $pk . '.jpg'; 
} 
else 
{
    return 'removed.jpg';
}

Now, this still leaves you with a bunch of problems.

• Unless you are validating the $pic_url properly, you are leaving yourself open for security vulnerabilities. What if the user inputs a relative path to a local file?
• file_get_contents() will throw a warning if the file cannot be found. Normally, you would deal with this by checking file_exists() first, but this is NOT possible here, because the http: wrapper does not support file_exists(). Therefore you can supress the error with @ before file_get_contents(). Suppressing errors like this should be avoided in most cases.
• Even if you suppress the error with '@', the call to file_get_contents() may still take some time - if the address is wrong, it may result in getting no reply from a server, which will cause it to hit a timeout (probably 30 seconds) during which time your script does not run and therefore an end user can get no feedback. This should be taken into account in your app.