resize and unlink file question

On my resize function. I am trying to unlink with my width and height size add on to the new file.

When it creates a new file it stores it in my images > cache folder and then addes width and height on to it.

example_100x50.jpg but the original file would be example.jpg the original files are located in images > catalog

If the example.jpg file is not there in folder then I need to be able to unlink that image but because it has the width and height added on to it I do not know how to make sure it unlinks correct one.

Question how could I unlink the correct cache image even though it has width and height different to the original image

PHP Code:

public function resize($filename, $width, $height) { 
    $this->load->library('image_lib');

    $old_file = FCPATH . 'images/' . $filename;

    $extension = pathinfo($filename, PATHINFO_EXTENSION);

    $extended_image = substr($filename, 0, strrpos($filename, '.')) . '_' . $width . 'x' . $height . '.' . $extension;
        
    $new_file = FCPATH . 'images/cache/' . $extended_image;

    // Checks if file does not exist in images folder but exist in cache will remove it.

    $check_if_file_is_set = array_reverse(glob(FCPATH  . 'images/catalog/*.{jpg,jpeg,png,gif,JPG,JPEG,PNG,GIF}', GLOB_BRACE));

    for ($i=0; $i < count($check_if_file_is_set); $i++) { 
        if ($i < sizeof($check_if_file_is_set)) {
                
        $file = str_replace(FCPATH . 'images/', '', $check_if_file_is_set[$i]);

            if (!file_exists(FCPATH . 'images/' . $file)) {
                // unlink(FCPATH . 'images/cache/' . $some_variable);
            }
        }
    }

    if (!is_file($new_file) || (filectime($old_file) > filectime($new_file))) {

        if (!is_dir($old_file)) {
            @mkdir(FCPATH . 'images/cache/'. dirname($filename), 0777);
        }
            
        $config['image_library'] = 'gd2';
        $config['source_image'] = $old_file;
        $config['maintain_ratio'] = FALSE;
        $config['width'] = $width;
        $config['height'] = $height;
        $config['new_image'] = $new_file;

        $this->image_lib->clear();
        $this->image_lib->initialize($config);
        $this->image_lib->resize();

    }

    $ouput_image = '';

    return base_url('images/cache/' . $extended_image);
} 


There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!