diff --git a/src/Psl/Internal/Loader.php b/src/Psl/Internal/Loader.php
index 31f9871..1849964 100644
--- a/src/Psl/Internal/Loader.php
+++ b/src/Psl/Internal/Loader.php
@@ -215,6 +215,7 @@ final class Loader
         'Psl\Str\Byte\search',
         'Psl\Str\Byte\search_ci',
         'Psl\Str\Byte\search_last',
+        'Psl\Str\Byte\search_last_ci',
         'Psl\Str\Byte\shuffle',
         'Psl\Str\Byte\slice',
         'Psl\Str\Byte\splice',
@@ -229,6 +230,14 @@ final class Loader
         'Psl\Str\Byte\uppercase',
         'Psl\Str\Byte\words',
         'Psl\Str\Byte\wrap',
+        'Psl\Str\Byte\after',
+        'Psl\Str\Byte\after_ci',
+        'Psl\Str\Byte\after_last',
+        'Psl\Str\Byte\after_last_ci',
+        'Psl\Str\Byte\before',
+        'Psl\Str\Byte\before_ci',
+        'Psl\Str\Byte\before_last',
+        'Psl\Str\Byte\before_last_ci',
         'Psl\Str\capitalize',
         'Psl\Str\capitalize_words',
         'Psl\Str\chr',
@@ -278,6 +287,14 @@ final class Loader
         'Psl\Str\uppercase',
         'Psl\Str\width',
         'Psl\Str\wrap',
+        'Psl\Str\after',
+        'Psl\Str\after_ci',
+        'Psl\Str\after_last',
+        'Psl\Str\after_last_ci',
+        'Psl\Str\before',
+        'Psl\Str\before_ci',
+        'Psl\Str\before_last',
+        'Psl\Str\before_last_ci',
         'Psl\invariant',
         'Psl\invariant_violation',
         'Psl\sequence',
@@ -353,6 +370,14 @@ final class Loader
         'Psl\Str\Grapheme\starts_with_ci',
         'Psl\Str\Grapheme\strip_prefix',
         'Psl\Str\Grapheme\strip_suffix',
+        'Psl\Str\Grapheme\after',
+        'Psl\Str\Grapheme\after_ci',
+        'Psl\Str\Grapheme\after_last',
+        'Psl\Str\Grapheme\after_last_ci',
+        'Psl\Str\Grapheme\before',
+        'Psl\Str\Grapheme\before_ci',
+        'Psl\Str\Grapheme\before_last',
+        'Psl\Str\Grapheme\before_last_ci',
     ];
 
     public const INTERFACES = [
diff --git a/src/Psl/Str/Byte/after.php b/src/Psl/Str/Byte/after.php
new file mode 100644
index 0000000..7132bf9
--- /dev/null
+++ b/src/Psl/Str/Byte/after.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after(string $haystack, string $needle, int $offset = 0): ?string
+{
+    $offset = search($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Byte/after_ci.php b/src/Psl/Str/Byte/after_ci.php
new file mode 100644
index 0000000..058b01d
--- /dev/null
+++ b/src/Psl/Str/Byte/after_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_ci($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Byte/after_last.php b/src/Psl/Str/Byte/after_last.php
new file mode 100644
index 0000000..991a2b4
--- /dev/null
+++ b/src/Psl/Str/Byte/after_last.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_last($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Byte/after_last_ci.php b/src/Psl/Str/Byte/after_last_ci.php
new file mode 100644
index 0000000..4136c73
--- /dev/null
+++ b/src/Psl/Str/Byte/after_last_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_last_ci($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Byte/before.php b/src/Psl/Str/Byte/before.php
new file mode 100644
index 0000000..2ccf8cd
--- /dev/null
+++ b/src/Psl/Str/Byte/before.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Byte/before_ci.php b/src/Psl/Str/Byte/before_ci.php
new file mode 100644
index 0000000..374ca6c
--- /dev/null
+++ b/src/Psl/Str/Byte/before_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_ci($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Byte/before_last.php b/src/Psl/Str/Byte/before_last.php
new file mode 100644
index 0000000..56c98d8
--- /dev/null
+++ b/src/Psl/Str/Byte/before_last.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_last($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Byte/before_last_ci.php b/src/Psl/Str/Byte/before_last_ci.php
new file mode 100644
index 0000000..27aa1b8
--- /dev/null
+++ b/src/Psl/Str/Byte/before_last_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_last_ci($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Byte/search_last_ci.php b/src/Psl/Str/Byte/search_last_ci.php
new file mode 100644
index 0000000..03a94b7
--- /dev/null
+++ b/src/Psl/Str/Byte/search_last_ci.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Byte;
+
+use Psl;
+
+/**
+ * Returns the last position of the 'needle' string in the 'haystack' string,
+ * or null if it isn't found (case-insensitive).
+ *
+ * An optional offset determines where in the haystack (from the beginning) the
+ * search begins. If the offset is negative, the search will begin that many
+ * characters from the end of the string and go backwards. If the offset is
+ * out-of-bounds, an InvariantViolationException will be thrown.
+ *
+ * @psalm-pure
+ *
+ * @throws Psl\Exception\InvariantViolationException If $offset is out-of-bounds.
+ */
+function search_last_ci(string $haystack, string $needle, int $offset = 0): ?int
+{
+    $haystack_length = length($haystack);
+    Psl\invariant($offset >= -$haystack_length && $offset <= $haystack_length, 'Offset is out-of-bounds.');
+
+    return false === ($pos = strripos($haystack, $needle, $offset)) ? null : $pos;
+}
diff --git a/src/Psl/Str/Grapheme/after.php b/src/Psl/Str/Grapheme/after.php
new file mode 100644
index 0000000..dc43fd4
--- /dev/null
+++ b/src/Psl/Str/Grapheme/after.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after(string $haystack, string $needle, int $offset = 0): ?string
+{
+    $offset = search($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Grapheme/after_ci.php b/src/Psl/Str/Grapheme/after_ci.php
new file mode 100644
index 0000000..ff8d41e
--- /dev/null
+++ b/src/Psl/Str/Grapheme/after_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_ci($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Grapheme/after_last.php b/src/Psl/Str/Grapheme/after_last.php
new file mode 100644
index 0000000..428724f
--- /dev/null
+++ b/src/Psl/Str/Grapheme/after_last.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_last($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Grapheme/after_last_ci.php b/src/Psl/Str/Grapheme/after_last_ci.php
new file mode 100644
index 0000000..3381199
--- /dev/null
+++ b/src/Psl/Str/Grapheme/after_last_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function after_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $offset = search_last_ci($haystack, $needle, $offset);
+    if (null === $offset) {
+        return null;
+    }
+
+        $offset += length($needle);
+
+    return slice($haystack, $offset, null);
+}
diff --git a/src/Psl/Str/Grapheme/before.php b/src/Psl/Str/Grapheme/before.php
new file mode 100644
index 0000000..d89d8cc
--- /dev/null
+++ b/src/Psl/Str/Grapheme/before.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Grapheme/before_ci.php b/src/Psl/Str/Grapheme/before_ci.php
new file mode 100644
index 0000000..29095ce
--- /dev/null
+++ b/src/Psl/Str/Grapheme/before_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_ci($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Grapheme/before_last.php b/src/Psl/Str/Grapheme/before_last.php
new file mode 100644
index 0000000..f731e52
--- /dev/null
+++ b/src/Psl/Str/Grapheme/before_last.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_last($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/Grapheme/before_last_ci.php b/src/Psl/Str/Grapheme/before_last_ci.php
new file mode 100644
index 0000000..6284642
--- /dev/null
+++ b/src/Psl/Str/Grapheme/before_last_ci.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str\Grapheme;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ *
+ * @psalm-pure
+ */
+function before_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0
+): ?string {
+    $length = search_last_ci($haystack, $needle, $offset);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length);
+}
diff --git a/src/Psl/Str/after.php b/src/Psl/Str/after.php
new file mode 100644
index 0000000..903394a
--- /dev/null
+++ b/src/Psl/Str/after.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $offset = search($haystack, $needle, $offset, $encoding);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null, $encoding);
+}
diff --git a/src/Psl/Str/after_ci.php b/src/Psl/Str/after_ci.php
new file mode 100644
index 0000000..cb13070
--- /dev/null
+++ b/src/Psl/Str/after_ci.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $offset = search_ci($haystack, $needle, $offset, $encoding);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null, $encoding);
+}
diff --git a/src/Psl/Str/after_last.php b/src/Psl/Str/after_last.php
new file mode 100644
index 0000000..59772de
--- /dev/null
+++ b/src/Psl/Str/after_last.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $offset = search_last($haystack, $needle, $offset, $encoding);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null, $encoding);
+}
diff --git a/src/Psl/Str/after_last_ci.php b/src/Psl/Str/after_last_ci.php
new file mode 100644
index 0000000..20a814f
--- /dev/null
+++ b/src/Psl/Str/after_last_ci.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function after_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $offset = search_last_ci($haystack, $needle, $offset, $encoding);
+    if (null === $offset) {
+        return null;
+    }
+
+    $offset += length($needle);
+
+    return slice($haystack, $offset, null, $encoding);
+}
diff --git a/src/Psl/Str/before.php b/src/Psl/Str/before.php
new file mode 100644
index 0000000..78a0e5b
--- /dev/null
+++ b/src/Psl/Str/before.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function before(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $length = search($haystack, $needle, $offset, $encoding);
+    if (null === $length) {
+        return null;
+    }
+
+    $length += length($needle);
+
+    return slice($haystack, 0, $length, $encoding);
+}
diff --git a/src/Psl/Str/before_ci.php b/src/Psl/Str/before_ci.php
new file mode 100644
index 0000000..f7f6e68
--- /dev/null
+++ b/src/Psl/Str/before_ci.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function before_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $length = search_ci($haystack, $needle, $offset, $encoding);
+    if (null === $length) {
+        return null;
+    }
+
+    $length += length($needle);
+
+    return slice($haystack, 0, $length, $encoding);
+}
diff --git a/src/Psl/Str/before_last.php b/src/Psl/Str/before_last.php
new file mode 100644
index 0000000..bdf714c
--- /dev/null
+++ b/src/Psl/Str/before_last.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function before_last(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $length = search_last($haystack, $needle, $offset, $encoding);
+    if (null === $length) {
+        return null;
+    }
+
+    $length += length($needle);
+
+    return slice($haystack, 0, $length, $encoding);
+}
diff --git a/src/Psl/Str/before_last_ci.php b/src/Psl/Str/before_last_ci.php
new file mode 100644
index 0000000..17f33ba
--- /dev/null
+++ b/src/Psl/Str/before_last_ci.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Str;
+
+use Psl;
+
+/**
+ * @throws Psl\Exception\InvariantViolationException If the $offset is out-of-bounds.
+ * @throws Psl\Exception\InvariantViolationException If an invalid $encoding is provided.
+ *
+ * @psalm-pure
+ */
+function before_last_ci(
+    string $haystack,
+    string $needle,
+    int $offset = 0,
+    ?string $encoding = null
+): ?string {
+    $length = search_last_ci($haystack, $needle, $offset, $encoding);
+    if (null === $length) {
+        return null;
+    }
+
+        $length += length($needle);
+
+    return slice($haystack, 0, $length, $encoding);
+}
diff --git a/tests/Psl/Str/AfterCiTest.php b/tests/Psl/Str/AfterCiTest.php
new file mode 100644
index 0000000..be43058
--- /dev/null
+++ b/tests/Psl/Str/AfterCiTest.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Str;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Str;
+
+final class AfterCiTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testAfter(
+        ?string $expected,
+        string $haystack,
+        string $needle,
+        int $offset,
+        ?string $encoding
+    ): void {
+        static::assertSame($expected, Str\after_ci($haystack, $needle, $offset, $encoding));
+    }
+
+    public function provideData(): array
+    {
+        return [
+            [null, '', '',  0, null],
+            ['orld!', 'Hello, World!', 'W', 0, null],
+            ['!', '🤷!', '🤷', 0, null],
+            [null, 'مرحبا بكم', '', 0, null],
+            [null, 'مرحبا بكم', 'ß', 0, null],
+            [', wôrld!', 'héllö, wôrld!', 'héllö', 0, null],
+            [', wôrld!', 'ḫéllö, wôrld!', 'ḫéllö', 0, null],
+            [', wôrld!', 'ḫéllö, wôrld!', 'Ḫéllö', 0, null],
+            [', wôrld!', 'Ḫéllö, wôrld!', 'Ḫéllö', 0, null],
+            [', wôrld!', 'Ḫéllö, wôrld!', 'ḫéllö', 0, null],
+            ['好', '你好', '你', 0, null],
+            ['にちは世界', 'こんにちは世界', 'こん', 0, null],
+            ['สดี', 'สวัสดี', 'วั', 0, null],
+            [', world!', 'Hello, world!', 'o', 0, null],
+            ['rld!', 'Hello, world!', 'o', 7, null],
+        ];
+    }
+}
diff --git a/tests/Psl/Str/AfterTest.php b/tests/Psl/Str/AfterTest.php
new file mode 100644
index 0000000..96128bc
--- /dev/null
+++ b/tests/Psl/Str/AfterTest.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Str;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Str;
+
+final class AfterTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testAfter(
+        ?string $expected,
+        string $haystack,
+        string $needle,
+        int $offset,
+        ?string $encoding
+    ): void {
+        static::assertSame($expected, Str\after($haystack, $needle, $offset, $encoding));
+    }
+
+
+    public function provideData(): array
+    {
+        return [
+            [null, '', '',  0, null],
+            ['orld!', 'Hello, World!', 'W', 0, null],
+            ['!', '🤷!', '🤷', 0, null],
+            [null, 'مرحبا بكم', '', 0, null],
+            [null, 'مرحبا بكم', 'ß', 0, null],
+            [', wôrld!', 'héllö, wôrld!', 'héllö', 0, null],
+            [', wôrld!', 'ḫéllö, wôrld!', 'ḫéllö', 0, null],
+            [null, 'ḫéllö, wôrld!', 'Ḫéllö', 0, null],
+            [', wôrld!', 'Ḫéllö, wôrld!', 'Ḫéllö', 0, null],
+            [null, 'Ḫéllö, wôrld!', 'ḫéllö', 0, null],
+            ['好', '你好', '你', 0, null],
+            ['にちは世界', 'こんにちは世界', 'こん', 0, null],
+            ['สดี', 'สวัสดี', 'วั', 0, null],
+            [', world!', 'Hello, world!', 'o', 0, null],
+            ['rld!', 'Hello, world!', 'o', 7, null],
+        ];
+    }
+}