Cron PHP Image Crop Left Justify

I need a PHP script that will take each .JPG file in the images/ subdirectory and do the following: 1. Check current file date and image width dimensions 2. If the file date = today's date AND current image width > 318pixels, then crop to 318 width, left-justify the crop, discard right side. 3. Image height needs to stay the same. 4. Re-save and overwrite the original .JPG file as the same file name, case-sensitive. 5. Loop through all .JPG files with today's date. Notes: The date of the file needs to be easily accessible in a var so I can change it to run manually on dates as needed. Please see attached sample image The script will be run as a cron job.