diff --git a/src/Concerns/DetectsEndpoints.php b/src/Concerns/DetectsEndpoints.php
index e9947d3..bc05388 100644
--- a/src/Concerns/DetectsEndpoints.php
+++ b/src/Concerns/DetectsEndpoints.php
@@ -2,6 +2,9 @@
 
 namespace Cerbero\JsonParser\Concerns;
 
+use function is_array;
+use function in_array;
+
 /**
  * The trait to detect endpoints.
  *
diff --git a/src/Decoders/ConfigurableDecoder.php b/src/Decoders/ConfigurableDecoder.php
index 13b7b46..58de8b9 100644
--- a/src/Decoders/ConfigurableDecoder.php
+++ b/src/Decoders/ConfigurableDecoder.php
@@ -4,6 +4,8 @@ namespace Cerbero\JsonParser\Decoders;
 
 use Cerbero\JsonParser\Config;
 
+use function call_user_func;
+
 /**
  * The configurable decoder.
  *
diff --git a/src/Pointers/Pointer.php b/src/Pointers/Pointer.php
index a1a879c..89d5540 100644
--- a/src/Pointers/Pointer.php
+++ b/src/Pointers/Pointer.php
@@ -7,6 +7,11 @@ use Cerbero\JsonParser\Tree;
 use Closure;
 use Stringable;
 
+use function count;
+use function call_user_func;
+use function is_int;
+use function array_slice;
+
 /**
  * The JSON pointer.
  *
diff --git a/src/Pointers/Pointers.php b/src/Pointers/Pointers.php
index 8063918..b689e0d 100644
--- a/src/Pointers/Pointers.php
+++ b/src/Pointers/Pointers.php
@@ -4,6 +4,8 @@ namespace Cerbero\JsonParser\Pointers;
 
 use Cerbero\JsonParser\Tree;
 
+use function count;
+
 /**
  * The JSON pointers collection.
  *
diff --git a/src/Progress.php b/src/Progress.php
index ac1c0d0..83b5719 100644
--- a/src/Progress.php
+++ b/src/Progress.php
@@ -2,6 +2,8 @@
 
 namespace Cerbero\JsonParser;
 
+use function is_null;
+
 /**
  * The parsing progress.
  *
diff --git a/src/Sources/Endpoint.php b/src/Sources/Endpoint.php
index 34d7b8e..868a165 100644
--- a/src/Sources/Endpoint.php
+++ b/src/Sources/Endpoint.php
@@ -8,6 +8,8 @@ use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\UriInterface;
 use Traversable;
 
+use function is_string;
+
 /**
  * The endpoint source.
  *
diff --git a/src/Sources/Filename.php b/src/Sources/Filename.php
index 349d439..e357946 100644
--- a/src/Sources/Filename.php
+++ b/src/Sources/Filename.php
@@ -4,6 +4,8 @@ namespace Cerbero\JsonParser\Sources;
 
 use Traversable;
 
+use function is_string;
+
 /**
  * The filename source.
  *
diff --git a/src/Sources/IterableSource.php b/src/Sources/IterableSource.php
index 944597e..383020f 100644
--- a/src/Sources/IterableSource.php
+++ b/src/Sources/IterableSource.php
@@ -4,6 +4,9 @@ namespace Cerbero\JsonParser\Sources;
 
 use Traversable;
 
+use function is_array;
+use function count;
+
 /**
  * The iterable source.
  *
diff --git a/src/Sources/Json.php b/src/Sources/Json.php
index c9e6303..edc27a2 100644
--- a/src/Sources/Json.php
+++ b/src/Sources/Json.php
@@ -5,6 +5,9 @@ namespace Cerbero\JsonParser\Sources;
 use Cerbero\JsonParser\Concerns\DetectsEndpoints;
 use Traversable;
 
+use function is_string;
+use function strlen;
+
 /**
  * The JSON source.
  *
diff --git a/src/Sources/JsonResource.php b/src/Sources/JsonResource.php
index 635f474..ef4e601 100644
--- a/src/Sources/JsonResource.php
+++ b/src/Sources/JsonResource.php
@@ -4,6 +4,9 @@ namespace Cerbero\JsonParser\Sources;
 
 use Traversable;
 
+use function is_string;
+use function is_resource;
+
 /**
  * The resource source.
  *
diff --git a/src/Sources/Psr7Stream.php b/src/Sources/Psr7Stream.php
index 3f28d92..f3c2604 100644
--- a/src/Sources/Psr7Stream.php
+++ b/src/Sources/Psr7Stream.php
@@ -5,6 +5,8 @@ namespace Cerbero\JsonParser\Sources;
 use Psr\Http\Message\StreamInterface;
 use Traversable;
 
+use function in_array;
+
 /**
  * The PSR-7 stream source.
  *
diff --git a/src/State.php b/src/State.php
index fb2a800..5c42c00 100644
--- a/src/State.php
+++ b/src/State.php
@@ -6,6 +6,8 @@ use Cerbero\JsonParser\Pointers\Pointer;
 use Cerbero\JsonParser\Pointers\Pointers;
 use Cerbero\JsonParser\Tokens\Token;
 
+use function is_string;
+
 /**
  * The JSON parsing state.
  *
diff --git a/src/Tree.php b/src/Tree.php
index c59a33d..01d2dca 100644
--- a/src/Tree.php
+++ b/src/Tree.php
@@ -2,6 +2,9 @@
 
 namespace Cerbero\JsonParser;
 
+use function is_int;
+use function is_string;
+
 /**
  * The JSON tree.
  *