How to check if $_POST[image] is set

Re asking how to check if $_POST[FILE] isset I have a file input and if I submit my form without an image I want something to happen if I uploaded a file in the input I want something different to happen.

if (!isset($_POST[image])) { }

seems to trigger regardless of whether or not I have uploaded a file in the input or not.

<label>
    <p>Profile Picture:</p>
    <input type="file" name="image" value="" />
</label>

My last question was marked as a duplicate of this answer Check whether file is uploaded however

if (!file_exists($_FILE['image'])) { }

didn't work either it is still showing truthy even when an image is uploaded. So not the answer I need.

To check if there is a file uploaded is you need to check the size of the file.

Then to check if its an image or not is you need to use the getimagesize() function. See my script below:

HTML:

<form action="index.php?act=s" method="post" enctype="multipart/form-data">
<input type="file" name="image" value=""/>
<input type="submit">
</form>

PHP:

<?php  
if(isset($_GET['act'])){
    // Check if there is a file uploaded
    if($_FILES["image"]["size"]>0){
        echo "There is a file uploaded<br>";
        // Check if its an image
            $check_if_image = getimagesize($_FILES["image"]["tmp_name"]);
            if($check_if_image !== false) {
                echo "Image = " . $check_if_image["mime"] . ".";            
            } else {
                echo "Not an image";            
            }
    }
    else{
        echo "There is NO file uploaded<br>";
    }   
}   
?>