Add iterable tests

Zend/tests/type_declarations/iterable_001.phpt

@@ -0,0 +1,48 @@
+--TEST--
+iterable type#001
+--FILE--
+<?php
+
+function test(iterable $iterable) {
+    var_dump($iterable);
+}
+
+function gen() {
+    yield 1;
+    yield 2;
+    yield 3;
+};
+
+test([1, 2, 3]);
+test(gen());
+test(new ArrayIterator([1, 2, 3]));
+
+try {
+    test(1);
+} catch (Throwable $e) {
+    echo $e->getMessage();
+}
+
+--EXPECTF--
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  [2]=>
+  int(3)
+}
+object(Generator)#1 (0) {
+}
+object(ArrayIterator)#1 (1) {
+  ["storage":"ArrayIterator":private]=>
+  array(3) {
+    [0]=>
+    int(1)
+    [1]=>
+    int(2)
+    [2]=>
+    int(3)
+  }
+}
+Argument 1 passed to test() must be iterable, integer given, called in %s on line %d

Zend/tests/type_declarations/iterable_002.phpt

@@ -0,0 +1,21 @@
+--TEST--
+iterable type#002 - Default values
+--FILE--
+<?php
+
+function foo(iterable $iterable = null) {
+    // Null should be allowed as a default value
+}
+
+function bar(iterable $iterable = []) {
+    // Array should be allowed as a default value
+}
+
+function baz(iterable $iterable = 1) {
+    // No other values should be allowed as defaults
+}
+
+?>
+--EXPECTF--
+
+Fatal error: Default value for parameters with iterable type can only be an array or NULL in %s on line %d

Zend/tests/type_declarations/iterable_003.phpt

@@ -0,0 +1,32 @@
+--TEST--
+iterable type#003 - Return types
+--FILE--
+<?php
+
+function foo(): iterable {
+	return [];
+}
+function bar(): iterable {
+	return (function () { yield; })();
+}
+
+function baz(): iterable {
+    return 1;
+}
+
+var_dump(foo());
+var_dump(bar());
+
+try {
+    baz();
+} catch (Throwable $e) {
+    echo $e->getMessage();
+}
+
+?>
+--EXPECT--
+array(0) {
+}
+object(Generator)#2 (0) {
+}
+Return value of baz() must be iterable, integer returned

ext/standard/tests/general_functions/is_iterable.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Test is_iterable() function
+--FILE--
+<?php
+
+function gen() {
+    yield;
+}
+
+var_dump(is_iterable([1, 2, 3]));
+var_dump(is_iterable(new ArrayIterator([1, 2, 3])));
+var_dump(is_iterable(gen()));
+var_dump(is_iterable(1));
+var_dump(is_iterable(3.14));
+var_dump(is_iterable(new stdClass()));
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
+bool(true)
+bool(false)
+bool(false)
+bool(false)