RepeatedField: unset by index (#11425)

Instead of using `array_pop()` to remove last element use `unset()` to remove by index

Closes #11425

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/11425 from Leprechaunz:unset-by-index a47fba57e4
PiperOrigin-RevId: 508691545

php/ext/google/protobuf/array.c

@@ -406,13 +406,13 @@ PHP_METHOD(RepeatedField, offsetUnset) {
     return;
   }
 
-  if (size == 0 || index != size - 1) {
+  if (size == 0 || index < 0 || index >= size) {
     php_error_docref(NULL, E_USER_ERROR, "Cannot remove element at %ld.\n",
                      index);
     return;
   }
 
-  upb_Array_Resize(intern->array, size - 1, Arena_Get(&intern->arena));
+  upb_Array_Delete(intern->array, index, 1);
 }
 
 /**

php/src/Google/Protobuf/Internal/RepeatedField.php

@@ -219,13 +219,13 @@ class RepeatedField implements \ArrayAccess, \IteratorAggregate, \Countable
     public function offsetUnset($offset)
     {
         $count = count($this->container);
-        if (!is_numeric($offset) || $count === 0 || $offset !== $count - 1) {
+        if (!is_numeric($offset) || $count === 0 || $offset < 0 || $offset >= $count) {
             trigger_error(
                 "Cannot remove element at the given index",
                 E_USER_ERROR);
             return;
         }
-        array_pop($this->container);
+        array_splice($this->container, $offset, 1);
     }
 
     /**

php/tests/ArrayTest.php

@@ -655,4 +655,31 @@ class ArrayTest extends TestBase
         $arr2 = clone $arr;
         $this->assertSame($arr[0], $arr2[0]);
     }
+
+    #########################################################
+    # Test offsetUnset
+    #########################################################
+
+    public function testOffsetUnset()
+    {
+        $arr = new RepeatedField(GPBType::INT32);
+        $arr[] = 0;
+        $arr[] = 1;
+        $arr[] = 2;
+
+        $this->assertSame(3, count($arr));
+        $this->assertSame(0, $arr[0]);
+        $this->assertSame(1, $arr[1]);
+        $this->assertSame(2, $arr[2]);
+
+        $arr->offsetUnset(1);
+        $this->assertSame(0, $arr[0]);
+        $this->assertSame(2, $arr[1]);
+
+        $arr->offsetUnset(0);
+        $this->assertSame(2, $arr[0]);
+
+        $arr->offsetUnset(0);
+        $this->assertCount(0, $arr);
+    }
 }