Reverting checks to original structure, changing only the error messages

Author: CViniciusSDias

ext/standard/string.c

@@ -1033,23 +1033,23 @@ PHP_FUNCTION(implode)
 		Z_PARAM_ARRAY_HT_OR_NULL(pieces)
 	ZEND_PARSE_PARAMETERS_END();
 
-	if (arg1_str != NULL && pieces == NULL) {
-		zend_type_error(
-			"%s(): If argument #1 ($separator) is of type string, "
-			"argument #2 ($array) must be of type array, null given",
-			get_active_function_name()
-		);
-		RETURN_THROWS();
-	}
-
-	if (pieces != NULL && arg1_str == NULL) {
-		zend_argument_type_error(1, "must be of type string, array given");
-		RETURN_THROWS();
-	}
-
 	if (pieces == NULL) {
+		if (arg1_array == NULL) {
+			zend_type_error(
+				"%s(): If argument #1 ($separator) is of type string, "
+				"argument #2 ($array) must be of type array, null given",
+				get_active_function_name()
+			);
+			RETURN_THROWS();
+		}
+
 		arg1_str = ZSTR_EMPTY_ALLOC();
 		pieces = arg1_array;
+	} else {
+		if (arg1_str == NULL) {
+			zend_argument_type_error(1, "must be of type string, array given");
+			RETURN_THROWS();
+		}
 	}
 
 	php_implode(arg1_str, pieces, return_value);