Import global functions and constants for enhanced performance

This is better for performance because these then don't need to be reevaluated every time they are called.

When encountering an unqualified function or constant reference, PHP will first try to locate a symbol in the current namespace by that name, and then fall back to the global namespace.
This short-circuits the check, which has substantial performance effects in some cases - in particular, ord(), chr() and strlen() show ~1500x faster calls when they are fully qualified.

However, this doesn't mean that PM is getting a massive amount faster. In real world terms, this translates to about 10-15% performance improvement.
But before anyone gets excited, you should know that the CodeOptimizer in the PreProcessor repo has been applying fully-qualified symbol optimizations to Jenkins builds for years, which is one of the reasons why Jenkins builds have better performance than home-built or source installations.
We're choosing to do this for the sake of future SafePHP integration and also to be able to get rid of the buggy CodeOptimizer, so that phar and source are more consistent.

src/pocketmine/inventory/ArmorInventory.php

@@ -29,6 +29,7 @@ use pocketmine\network\mcpe\protocol\InventoryContentPacket;
 use pocketmine\network\mcpe\protocol\InventorySlotPacket;
 use pocketmine\network\mcpe\protocol\MobArmorEquipmentPacket;
 use pocketmine\Player;
+use function array_merge;
 
 class ArmorInventory extends BaseInventory{
 	public const SLOT_HEAD = 0;

src/pocketmine/inventory/BaseInventory.php

@@ -32,6 +32,11 @@ use pocketmine\network\mcpe\protocol\InventoryContentPacket;
 use pocketmine\network\mcpe\protocol\InventorySlotPacket;
 use pocketmine\network\mcpe\protocol\types\ContainerIds;
 use pocketmine\Player;
+use function array_slice;
+use function count;
+use function max;
+use function min;
+use function spl_object_hash;
 
 abstract class BaseInventory implements Inventory{
 

src/pocketmine/inventory/ChestInventory.php

@@ -28,6 +28,7 @@ use pocketmine\network\mcpe\protocol\LevelSoundEventPacket;
 use pocketmine\network\mcpe\protocol\types\WindowTypes;
 use pocketmine\Player;
 use pocketmine\tile\Chest;
+use function count;
 
 class ChestInventory extends ContainerInventory{
 

src/pocketmine/inventory/CraftingGrid.php

@@ -25,6 +25,9 @@ namespace pocketmine\inventory;
 
 use pocketmine\item\Item;
 use pocketmine\Player;
+use function max;
+use function min;
+use const PHP_INT_MAX;
 
 class CraftingGrid extends BaseInventory{
 	public const SIZE_SMALL = 2;

src/pocketmine/inventory/CraftingManager.php

@@ -29,6 +29,12 @@ use pocketmine\network\mcpe\protocol\BatchPacket;
 use pocketmine\network\mcpe\protocol\CraftingDataPacket;
 use pocketmine\Server;
 use pocketmine\timings\Timings;
+use function array_map;
+use function file_get_contents;
+use function json_decode;
+use function json_encode;
+use function usort;
+use const DIRECTORY_SEPARATOR;
 
 class CraftingManager{
 	/** @var ShapedRecipe[][] */

src/pocketmine/inventory/DoubleChestInventory.php

@@ -26,6 +26,9 @@ namespace pocketmine\inventory;
 use pocketmine\item\Item;
 use pocketmine\Player;
 use pocketmine\tile\Chest;
+use function array_merge;
+use function array_slice;
+use function count;
 
 class DoubleChestInventory extends ChestInventory implements InventoryHolder{
 	/** @var ChestInventory */

src/pocketmine/inventory/PlayerInventory.php

@@ -30,6 +30,8 @@ use pocketmine\network\mcpe\protocol\InventoryContentPacket;
 use pocketmine\network\mcpe\protocol\MobEquipmentPacket;
 use pocketmine\network\mcpe\protocol\types\ContainerIds;
 use pocketmine\Player;
+use function in_array;
+use function is_array;
 
 class PlayerInventory extends BaseInventory{
 

src/pocketmine/inventory/ShapedRecipe.php

@@ -25,6 +25,12 @@ namespace pocketmine\inventory;
 
 use pocketmine\item\Item;
 use pocketmine\item\ItemFactory;
+use function array_map;
+use function array_values;
+use function count;
+use function implode;
+use function strlen;
+use function strpos;
 
 class ShapedRecipe implements CraftingRecipe{
 	/** @var string[] */

src/pocketmine/inventory/ShapelessRecipe.php

@@ -24,6 +24,8 @@ declare(strict_types=1);
 namespace pocketmine\inventory;
 
 use pocketmine\item\Item;
+use function array_map;
+use function count;
 
 class ShapelessRecipe implements CraftingRecipe{
 	/** @var Item[] */

src/pocketmine/inventory/transaction/CraftingTransaction.php

@@ -28,6 +28,9 @@ use pocketmine\inventory\CraftingRecipe;
 use pocketmine\item\Item;
 use pocketmine\network\mcpe\protocol\ContainerClosePacket;
 use pocketmine\network\mcpe\protocol\types\ContainerIds;
+use function array_pop;
+use function count;
+use function intdiv;
 
 class CraftingTransaction extends InventoryTransaction{
 	/** @var CraftingRecipe|null */

src/pocketmine/inventory/transaction/InventoryTransaction.php

@@ -29,6 +29,11 @@ use pocketmine\inventory\transaction\action\InventoryAction;
 use pocketmine\inventory\transaction\action\SlotChangeAction;
 use pocketmine\item\Item;
 use pocketmine\Player;
+use function assert;
+use function count;
+use function get_class;
+use function min;
+use function spl_object_hash;
 
 /**
  * This InventoryTransaction only allows doing Transaction between one / two inventories

src/pocketmine/inventory/transaction/action/SlotChangeAction.php

@@ -27,6 +27,7 @@ use pocketmine\inventory\Inventory;
 use pocketmine\inventory\transaction\InventoryTransaction;
 use pocketmine\item\Item;
 use pocketmine\Player;
+use function spl_object_hash;
 
 /**
  * Represents an action causing a change in an inventory slot.