Add DCE support for ARRAY_KEY_EXISTS

Author: nikic

ext/opcache/Optimizer/dce.c

@@ -124,6 +124,7 @@ static inline zend_bool may_have_side_effects(
 		case ZEND_IN_ARRAY:
 		case ZEND_FUNC_NUM_ARGS:
 		case ZEND_FUNC_GET_ARGS:
+		case ZEND_ARRAY_KEY_EXISTS:
 			/* No side effects */
 			return 0;
 		case ZEND_ROPE_END:

ext/opcache/Optimizer/zend_inference.c

@@ -4634,6 +4634,14 @@ int zend_may_throw(const zend_op *opline, const zend_op_array *op_array, zend_ss
 				default:
 					return 1;
 			}
+		case ZEND_ARRAY_KEY_EXISTS:
+			if ((t2 & MAY_BE_ANY) != MAY_BE_ARRAY) {
+				return 1;
+			}
+			if ((t1 & (MAY_BE_ARRAY|MAY_BE_OBJECT|MAY_BE_RESOURCE))) {
+				return 1;
+			}
+			return 0;
 		default:
 			return 1;
 	}