Doctrine Collections: ManyToMany, Forms & other Complex Relations

With the basic of Doctrine relations behind us, it's time to dive deeper and get our hands dirty with some real-world, but complex collections. Honestly, this is the hardest part of Doctrine: so let's get it right:

• Creating ManyToMany associations
• Querying on ManyToMany relations
• Mapping the inverse (collection) side of a relation
• (bonus) Using DoctrineExtension for clean URL slugs
• Keeping the owning & inverse sides in-sync
• Using orphanRemoval to delete items in a collection
• Using cascade to save items in a collection
• Counting collections in the EXTRA_LAZY way
• Rendering relationship data from both sides
• Filtering collections efficiently with Criteria (mind will be blown)
• Dealing with complex collection forms
• Adding "extra" data to the "join table"

Doctrine relationships take a little bit more work to get setup. So let's master this stuff, setup our relationships to win, and get back to work.

• Give me Clean URL Strings (slugs!)
• DoctrineExtensions: Sluggable
• Refactoring Carefully
• ManyToMany Relationship
• Inserting into a ManyToMany
• Fetching Items from a ManyToMany Collection
• ManyToMany: The Inverse Side of the Relationship
• Removing a ManyToMany Item
• Hooking up the Scientist Removal JavaScript
• ManyToMany & Fixtures
• Joining Across a ManyToMany + EXTRA_LAZY Fetch
• EntityType Checkboxes with ManyToMany
• Saving the Inverse Side of a ManyToMany
• Form by_reference + Adder and Remover
• Synchronizing Owning & Inverse Sides
• ManyToMany with Extra Fields
• Join Entity App Refactoring
• Using the new OneToMany Collections
• Embedded Form: CollectionType
• Collection Delete & allow_delete
• Deleting an Item from a Collection: orphanRemoval
• CollectionType: Adding New with the Prototype
• Adding to a Collection: Cascade Persist
• Embedded Form Validation with @Valid
• Customizing the Collection Form Prototype
• Form Events: A readonly Embedded Field
• Collection Filtering: The Easy Way
• Criteria System: Champion Collection Filtering