Use file_exists() and is_readable() to avoid load failures

When using PHP's imagecreatefromgd2() function to process GD2 images, if the target file does not exist, the path is wrong, or the file is unreadable, the program will throw a warning or even cause a crash. To enhance the robustness of the code, developers should use file_exists() and is_readable() for pre-checking before calling imagecreatefromgd2() .

Why do you need to check for file existence and readability?

PHP's imagecreatefromgd2() is a function specifically used to load GD2 format images. It depends on the integrity and access permissions of the underlying file. If the target file does not exist or is unreadable, it will trigger an error similar to the following:

 Warning: imagecreatefromgd2(): gd2: Input is not in GD2 format in ...

This error not only affects the user experience, but may also expose server path information, which poses certain security risks.

Sample code: Safely load GD2 images

 <?php

// Assume this is what you want to load GD2 Image path
$imagePath = '/var/www/m66.net/images/sample.gd2';

// use file_exists() and is_readable() To check whether the file exists and is readable
if (file_exists($imagePath) && is_readable($imagePath)) {
    // Safely try to load GD2 picture
    $image = @imagecreatefromgd2($imagePath);
    
    if ($image !== false) {
        echo "Image loading successfully！";
        // The image can be processed，For example, zoom、Display etc.
    } else {
        echo "Image format wrong or corrupted，Unable to create image resources。";
    }
} else {
    echo "The file does not exist or is not readable：" . htmlspecialchars($imagePath);
}
?>

Tips: Hide warning message

Even if the file_exists() and is_readable() check pass, imagecreatefromgd2() may still throw a warning in case of a malformed file. You can use the @ operator to suppress warnings (as shown in the above code), but the recommended approach is to combine the error logging system to facilitate post-tracking:

 $image = @imagecreatefromgd2($imagePath);
if ($image === false) {
    error_log("GD2 Image loading failed：" . $imagePath);
}

Summarize

Always using file_exists() and is_readable() are good defensive programming practices before calling imagecreatefromgd2() . It not only prevents runtime errors, but also improves the robustness and security of the application. These two functions are indispensable especially when dealing with image resources uploaded by users or stitched dynamic paths.