How to Determine If a File is an Image in PHP

Verifying the authenticity of an uploaded file as an image is crucial for security purposes. While checking the file extension may seem inadequate, PHP provides reliable methods for image verification.

getimagesize() Function

The getimagesize() function stands out as the most definitive solution for this task. It analyzes the file's contents and returns an array containing information about the image, including width, height, mime type, and other attributes:

if (@is_array(getimagesize($mediapath))) {
    $image = true;
} else {
    $image = false;
}

Here's a sample output from getimagesize():

Array (
[0] => 800
[1] => 450
[2] => 2
[3] => width="800" height="450"
[bits] => 8
[channels] => 3
[mime] => image/jpeg)

This array structure confirms that the file is an image, making getimagesize() a highly accurate method for image verification.