Specific use case wordpress image upload hook. Used to match image file names with csv file row values. Also uses WP Real Media Library to move files into specific sections depending on the image

custom_import_hook

function ph_image_upload_modification( $attachment_ID ) {

	// set up file name
	$filename   =   $_REQUEST['name'];
 	$withoutExt =   preg_replace('/\\.[^.\\s]{3,4}$/', '', $filename);
 	$withoutExt =   str_replace(array('-','_'), ' ', $withoutExt);

	// set line endings for csv file
	ini_set('auto_detect_line_endings',TRUE);

	// function handling getting csv file
	function readCSV($csvFile){
		$file_handle = fopen($csvFile, 'r');
		while (!feof($file_handle) ) {
			$line_of_text[] = fgetcsv($file_handle, 0);
		}
		fclose($file_handle);
		return $line_of_text;
	}
	 
	// get csv file
	$csv = readCSV(ABSPATH . 'product_image_assoc.csv'); // Make sure this exsists or you will have a forever error log.

	// go through csv file rows
	foreach ( $csv as $key => $c ) {
	    $firstColumn = $c[0];
	    $secondColumn = $c[1];

	    // if it matches a column, attach the description and break loop
	    if ($firstColumn === $withoutExt) {
			$my_post = array(
		        'ID'           => $attachment_ID,
		        'post_excerpt' => $withoutExt,  // caption
		        'post_content' => $secondColumn,  // description
		    );
		    wp_update_post( $my_post );

	    	$moved = wp_rml_move(1, array($attachment_ID));

	    	break;
	    }

	    // if it's the last row and it doesn't match this one, put in a secondary folder for manual proces
	    end($csv);
	    if ($key === key($csv) && $firstColumn !== $withoutExt) {
	        $moved = wp_rml_move(2, array($attachment_ID));
	    }
	}

}

add_filter( 'add_attachment', 'ph_image_upload_modification', 99999, 2 );