how to sort an entity's arrayCollection in symfony2

You should be able to use the @ORM\OrderBy statement which allows you to specify columns to order collections on:

/**
 * @ORM\OneToMany(targetEntity="BizTV\ContentManagementBundle\Entity\Content", mappedBy="container")
 * @ORM\OrderBy({"sort_order" = "ASC"})
 */
private $content;

In fact this may be a duplicate of How to OrderBy on OneToMany/ManyToOne

Edit

Checking for implementation advice it appears that you must fetch the tables with a join query to the collection in order for the @ORM\OrderBy annotation to work: http://www.krueckeberg.org/notes/d2.html

This means that you must write a method in the repository to return the container with the contents table joined.

If you want to be sure that you always get your relations in the order based on current property values, you can do something like this:

$sort = new Criteria(null, ['Order' => Criteria::ASC]);
return $this->yourCollectionProperty->matching($sort);

Use that for example if you've changed the Order property. Works great for a "Last modified date" as well.

You can write

@ORM\OrderBy({"date" = "ASC", "time" = "ASC"})

for multiple criteria ordering.