Use null-coalesce assignments

Author: alcaeus

src/Model/LazyBSONArray.php

@@ -159,12 +159,7 @@ public function offsetExists($offset): bool
 
         $offset = (int) $offset;
 
-        // If we've looked for the value, return the cached result
-        if (isset($this->exists[$offset])) {
-            return $this->exists[$offset];
-        }
-
-        return $this->exists[$offset] = $this->bson->has($offset);
+        return $this->exists[$offset] ??= $this->bson->has($offset);
     }
 
     /**

src/Model/LazyBSONDocument.php

@@ -127,12 +127,7 @@ public function __get(string $property)
 
     public function __isset(string $name): bool
     {
-        // If we've looked for the value, return the cached result
-        if (isset($this->exists[$name])) {
-            return $this->exists[$name];
-        }
-
-        return $this->exists[$name] = $this->bson->has($name);
+        return $this->exists[$name] ??= $this->bson->has($name);
     }
 
     /** @param TValue $value */