diff --git a/src/Parser/AssignOpTrait.php b/src/Parser/AssignOpTrait.php
index 4305914a..6e161de1 100644
--- a/src/Parser/AssignOpTrait.php
+++ b/src/Parser/AssignOpTrait.php
@@ -823,6 +823,13 @@ trait AssignOpTrait
 
     protected function parseAssignOp(Expr\AssignOp $node, string $op): string
     {
+        if ($node->var instanceof Expr\ArrayDimFetch
+            && !$this->canUpdateKnownArraySlotInPlace($node, $op)
+        ) {
+            $node = clone $node;
+            $node->var = $this->stabilizeAssignOpArrayAccess($node->var);
+        }
+
         $this->assertImmutableMutationTarget($node->var);
         $this->assertNativeArrayAccessDirectWrite($node->var, false);
         $this->assertNativeObjectOperatorOperandSupported($node->var, $node, $op);
@@ -869,7 +876,8 @@ trait AssignOpTrait
             return $nativePropertyAssignOp;
         }
 
-        $var          = $this->parseWritableIdentifier($node->var);
+        $arrayDimFetch = $this->isArrayDimFetch($node->var);
+        $var          = $arrayDimFetch ? '' : $this->parseWritableIdentifier($node->var);
         $expr         = $this->isAssignOpConcat($op) ? '' : (string) $this->parseIdentifier($node->expr);
 
         if ($this->isVarExpr($node->var)) {
@@ -906,7 +914,7 @@ trait AssignOpTrait
             return $var . ' ' . $op . ' ' . $rightExprStr;
         }
 
-        if ($this->isArrayDimFetch($node->var)) {
+        if ($arrayDimFetch) {
             if ($this->isStdContainerExpr($node->var)) {
                 return $this->parseStdContainerAssignOp($node, $op);
             }
@@ -926,7 +934,8 @@ trait AssignOpTrait
              * $tmp_var = $count[$r] - 1;
              * $count[$r] = $tmp_var;.
              */
-            $type      = $this->detectVarType($node->var);
+            $isGlobals = $this->isVarExpr($node->var->var) && $node->var->var->name === 'GLOBALS';
+            $type      = $isGlobals ? Type::VAR : $this->detectVarType($node->var);
             $rightType = $this->detectTypeOfExpr($node->expr);
             $tmpVar    = $this->genTmpVarName();
             // PHP arrays are dynamically typed even when SSA can currently
@@ -934,8 +943,9 @@ trait AssignOpTrait
             // Zend arithmetic promotes overflowing integers to float instead
             // of evaluating a signed C++ expression with undefined behavior.
             $this->addLocalVar($tmpVar, Type::VAR);
-            $dim      = $this->parseIdentifier($node->var->dim);
-            $readVar  = $this->parseArrayDimFetchRead($node->var);
+            $stableAccess = $node->var;
+            $dim = $this->parseIdentifier($node->var->dim);
+            $readVar  = $this->parseArrayDimFetchRead($stableAccess);
             $binaryOp = $this->removeAssignOp($op);
 
             if ($binaryOp === '.') {
@@ -953,10 +963,10 @@ trait AssignOpTrait
                     $this->convertExprType($expr, $type, $rightType) . ';';
             }
 
-            if ($this->isVarExpr($node->var->var) && $node->var->var->name === 'GLOBALS') {
-                return $var . ' = ' . $tmpVar;
+            if ($isGlobals) {
+                return $this->parseGlobalsArrayDimFetch($stableAccess) . ' = ' . $tmpVar;
             }
-            return '(' . $this->parseArrayDimStore($node->var->var, $dim, $tmpVar) . ', ' . $tmpVar . ')';
+            return '(' . $this->parseArrayDimStore($stableAccess->var, $dim, $tmpVar) . ', ' . $tmpVar . ')';
         }
 
         if ($this->isPropertyFetch($node->var) and !$this->isNativePropertyAccess($node->var)) {
@@ -990,6 +1000,41 @@ trait AssignOpTrait
         return $var . ' ' . $op . ' (' . $expr . ')';
     }
 
+    /**
+     * Evaluate every dynamic dimension of a compound-assignment target once,
+     * from the innermost access to the outermost access, before evaluating the
+     * right-hand side. Both the read and write lowering then reuse the cloned
+     * access path and cannot observe keys changed by a later dimension or RHS.
+     */
+    private function stabilizeAssignOpArrayAccess(Expr\ArrayDimFetch $access): Expr\ArrayDimFetch
+    {
+        $dimensions = [];
+        $base = $access;
+        while ($base instanceof Expr\ArrayDimFetch) {
+            $dimensions[] = $base;
+            $base = $base->var;
+        }
+
+        $stableAccess = $base;
+        foreach (array_reverse($dimensions) as $dimension) {
+            $dim = $dimension->dim;
+            $literal = $dim instanceof Node\Scalar\LNumber
+                || $dim instanceof Node\Scalar\DNumber
+                || $dim instanceof Node\Scalar\String_;
+            if ($dim !== null && !$literal) {
+                $tmp = $this->parseOrderedOperand($dim, false, true);
+                $dim = new Variable($tmp, $dim->getAttributes());
+            }
+            $stableAccess = new Expr\ArrayDimFetch(
+                $stableAccess,
+                $dim,
+                $dimension->getAttributes(),
+            );
+        }
+
+        return $stableAccess;
+    }
+
     /**
      * Preserve PHP's concat-assignment operation for statically typed strings.
      * String::append() calls concat_function() with the target as both the
diff --git a/src/Parser/BinaryOpTrait.php b/src/Parser/BinaryOpTrait.php
index f186acae..30b05b57 100644
--- a/src/Parser/BinaryOpTrait.php
+++ b/src/Parser/BinaryOpTrait.php
@@ -521,10 +521,10 @@ trait BinaryOpTrait
         return $this->parseOrderedOperand($expr, true);
     }
 
-    protected function parseOrderedOperand(NodeAbstract $expr, bool $numeric): string
+    protected function parseOrderedOperand(NodeAbstract $expr, bool $numeric, bool $forceMaterialize = false): string
     {
         $this->assertExprCanBeUsedAsValue($expr, 'operand');
-        if (!$this->shouldMaterializeOrderedOperand($expr)) {
+        if (!$forceMaterialize && !$this->shouldMaterializeOrderedOperand($expr)) {
             $value = $numeric ? $this->parseNumericIdentifier($expr) : $this->parseIdentifier($expr);
             return $this->normalizeNativeObjectValueExpr($expr, $value);
         }
diff --git a/tests/compiler/array/compound-offset-evaluated-once.phpt b/tests/compiler/array/compound-offset-evaluated-once.phpt
new file mode 100644
index 00000000..d2039286
--- /dev/null
+++ b/tests/compiler/array/compound-offset-evaluated-once.phpt
@@ -0,0 +1,92 @@
+--TEST--
+Array compound assignment evaluates a side-effecting offset once
+--FILE--
+<?php
+declare(strict_types=1);
+
+function nextCompoundOffset(int &$index): int
+{
+    return $index++;
+}
+
+function changeCompoundOffsetPart(string &$part): int
+{
+    $part = 'b';
+    return 5;
+}
+
+function main(): void
+{
+    $statementIndex = 0;
+    $statementValues = [10];
+    $statementValues[$statementIndex++] += 5;
+
+    var_dump($statementIndex, $statementValues);
+
+    $resultIndex = 0;
+    $resultValues = [20];
+    $result = ($resultValues[$resultIndex++] *= 2);
+
+    var_dump($resultIndex, $resultValues, $result);
+
+    $globalIndex = 0;
+    $GLOBALS['typephp_compound_once_0'] = 3;
+    $GLOBALS['typephp_compound_once_' . $globalIndex++] += 4;
+
+    var_dump($globalIndex, $GLOBALS['typephp_compound_once_0']);
+
+    $nestedIndex = 0;
+    $nestedValues = [[10, 20], [30, 40]];
+    $nestedResult = ($nestedValues[$nestedIndex++][$nestedIndex++] += 5);
+
+    var_dump($nestedIndex, $nestedValues[0][1], $nestedValues[1][0], $nestedResult);
+
+    $callIndex = 0;
+    $callValues = [[10, 20], [30, 40]];
+    $callResult = ($callValues[nextCompoundOffset($callIndex)][nextCompoundOffset($callIndex)] *= 2);
+
+    var_dump($callIndex, $callValues[0][1], $callValues[1][0], $callResult);
+
+    $rhsIndex = 0;
+    $rhsValues = [10, 20];
+    $rhsResult = ($rhsValues[$rhsIndex] += ++$rhsIndex);
+
+    var_dump($rhsIndex, $rhsValues[0], $rhsValues[1], $rhsResult);
+
+    $offsetPart = 'a';
+    $interpolatedValues = ['a0' => 10, 'b0' => 20];
+    $interpolatedResult = ($interpolatedValues["{$offsetPart}0"] += changeCompoundOffsetPart($offsetPart));
+
+    var_dump($offsetPart, $interpolatedValues['a0'], $interpolatedValues['b0'], $interpolatedResult);
+}
+?>
+--EXPECT--
+int(1)
+array(1) {
+  [0]=>
+  int(15)
+}
+int(1)
+array(1) {
+  [0]=>
+  int(40)
+}
+int(40)
+int(1)
+int(7)
+int(2)
+int(25)
+int(30)
+int(25)
+int(2)
+int(40)
+int(30)
+int(40)
+int(1)
+int(11)
+int(20)
+int(11)
+string(1) "b"
+int(15)
+int(20)
+int(15)
diff --git a/tests/compiler/std-vector/compound-offset-evaluated-once.phpt b/tests/compiler/std-vector/compound-offset-evaluated-once.phpt
new file mode 100644
index 00000000..e518490c
--- /dev/null
+++ b/tests/compiler/std-vector/compound-offset-evaluated-once.phpt
@@ -0,0 +1,21 @@
+--TEST--
+std vector compound assignment evaluates its offset before the RHS
+--FILE--
+<?php
+function main(): void
+{
+    $index = 0;
+    $vector = std::vector(Type::Int, 2);
+    $vector[0] = 10;
+    $vector[1] = 20;
+
+    $result = ($vector[$index] += ++$index);
+
+    var_dump($index, $vector[0], $vector[1], $result);
+}
+?>
+--EXPECT--
+int(1)
+int(11)
+int(20)
+int(11)