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nikicnikic
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Implement ??= operator
RFC: https://wiki.php.net/rfc/null_coalesce_equal_operator $a ??= $b is $a ?? ($a = $b), with the difference that $a is only evaluated once, to the degree that this is possible. In particular in $a[foo()] ?? $b function foo() is only ever called once. However, the variable access themselves will be reevaluated.
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‎UPGRADING

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@@ -90,6 +90,15 @@ PHP 7.4 UPGRADE NOTES
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This will enforce that $user->id can only be assigned integer and
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$user->name can only be assigned strings. For more information see the
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RFC: https://wiki.php.net/rfc/typed_properties_v2
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. Added support for coalesce assign (??=) operator. For example:
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$array['key'] ??= computeDefault();
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// is roughly equivalent to
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if (!isset($array['key'])) {
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$array['key'] = computeDefault();
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}
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RFC: https://wiki.php.net/rfc/null_coalesce_equal_operator
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- FFI:
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. A new extension which provides a simple way to call native functions, access

‎Zend/tests/assign_coalesce_001.phpt

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--TEST--
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Coalesce assign (??=): Basic behavior
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--FILE--
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<?php
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// Refcounted values
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$foo = "fo";
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$foo .= "o";
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$bar = "ba";
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$bar .= "r";
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// Identity function used to track single-evaluation
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function id($arg) {
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echo "id($arg)\n";
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return $arg;
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}
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echo "Simple variables:\n";
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$a = 123;
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$a ??= 456;
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var_dump($a);
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$b = null;
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$b ??= $foo;
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var_dump($b);
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$c = $foo;
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$c ??= $bar;
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var_dump($c);
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$d ??= $foo;
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var_dump($c);
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echo "\nArrays:\n";
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$ary = [];
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$ary["foo"] ??= 123;
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$ary[$foo] ??= $bar;
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$ary[$bar] ??= $foo;
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var_dump($ary);
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$ary = [];
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$ary[id($foo)] ??= 123;
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$ary[id($foo)] ??= $bar;
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$ary[id($bar)] ??= $foo;
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var_dump($ary);
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echo "\nObjects:\n";
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$obj = new stdClass;
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$obj->foo ??= 123;
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$obj->$foo ??= $bar;
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$obj->$bar ??= $foo;
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var_dump($obj);
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$obj = new stdClass;
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$obj->{id($foo)} ??= 123;
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$obj->{id($foo)} ??= $bar;
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$obj->{id($bar)} ??= $foo;
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var_dump($obj);
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class Test {
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public static $foo;
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public static $bar;
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}
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echo "\nStatic props:\n";
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Test::$foo ??= 123;
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Test::$$foo ??= $bar;
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Test::$$bar ??= $foo;
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var_dump(Test::$foo, Test::$bar);
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Test::$foo = null;
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Test::$bar = null;
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Test::${id($foo)} ??= 123;
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Test::${id($foo)} ??= $bar;
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Test::${id($bar)} ??= $foo;
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var_dump(Test::$foo, Test::$bar);
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?>
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--EXPECT--
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Simple variables:
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int(123)
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string(3) "foo"
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string(3) "foo"
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string(3) "foo"
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Arrays:
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array(2) {
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["foo"]=>
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int(123)
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["bar"]=>
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string(3) "foo"
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}
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id(foo)
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id(foo)
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id(bar)
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array(2) {
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["foo"]=>
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int(123)
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["bar"]=>
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string(3) "foo"
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}
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Objects:
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object(stdClass)#1 (2) {
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["foo"]=>
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int(123)
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["bar"]=>
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string(3) "foo"
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}
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id(foo)
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id(foo)
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id(bar)
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object(stdClass)#2 (2) {
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["foo"]=>
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int(123)
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["bar"]=>
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string(3) "foo"
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}
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Static props:
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int(123)
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string(3) "foo"
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id(foo)
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id(foo)
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id(bar)
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int(123)
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string(3) "foo"

‎Zend/tests/assign_coalesce_002.phpt

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--TEST--
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Coalesce assign (??=): Exception handling
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--FILE--
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<?php
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$foo = "fo";
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$foo .= "o";
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$bar = "ba";
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$bar .= "r";
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function id($arg) {
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echo "id($arg)\n";
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return $arg;
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}
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function do_throw($msg) {
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throw new Exception($msg);
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}
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$ary = [];
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try {
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$ary[id($foo)] ??= do_throw("ex1");
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} catch (Exception $e) {
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echo $e->getMessage(), "\n";
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}
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var_dump($ary);
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class AA implements ArrayAccess {
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public function offsetExists($k) {
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return true;
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}
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public function &offsetGet($k) {
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$var = ["foo" => "bar"];
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return $var;
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}
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public function offsetSet($k,$v) {}
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public function offsetUnset($k) {}
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}
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class Dtor {
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public function __destruct() {
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throw new Exception("dtor");
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}
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}
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$ary = new AA;
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try {
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$ary[new Dtor][id($foo)] ??= $bar;
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} catch (Exception $e) {
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echo $e->getMessage(), "\n";
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}
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var_dump($foo);
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class AA2 implements ArrayAccess {
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public function offsetExists($k) {
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return false;
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}
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public function offsetGet($k) {
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return null;
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}
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public function offsetSet($k,$v) {}
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public function offsetUnset($k) {}
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}
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$ary = ["foo" => new AA2];
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try {
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$ary[id($foo)][new Dtor] ??= $bar;
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} catch (Exception $e) {
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echo $e->getMessage(), "\n";
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}
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var_dump($foo);
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?>
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--EXPECT--
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id(foo)
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ex1
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array(0) {
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}
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id(foo)
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dtor
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string(3) "foo"
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id(foo)
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dtor
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string(3) "foo"

‎Zend/tests/assign_coalesce_003.phpt

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--TEST--
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Coalesce assign (??=): ArrayAccess handling
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--FILE--
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<?php
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function id($arg) {
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echo "id($arg)\n";
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return $arg;
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}
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class AA implements ArrayAccess {
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public $data;
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public function __construct($data = []) {
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$this->data = $data;
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}
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public function &offsetGet($k) {
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echo "offsetGet($k)\n";
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return $this->data[$k];
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}
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public function offsetExists($k) {
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echo "offsetExists($k)\n";
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return array_key_exists($k, $this->data);
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}
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public function offsetSet($k,$v) {
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echo "offsetSet($k,$v)\n";
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$this->data[$k] = $v;
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}
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public function offsetUnset($k) { }
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}
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$ary = new AA(["foo" => new AA, "null" => null]);
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echo "[foo]\n";
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$ary["foo"] ??= "bar";
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echo "[bar]\n";
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$ary["bar"] ??= "foo";
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echo "[null]\n";
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$ary["null"] ??= "baz";
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echo "[foo][bar]\n";
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$ary["foo"]["bar"] ??= "abc";
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echo "[foo][bar]\n";
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$ary["foo"]["bar"] ??= "def";
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?>
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--EXPECT--
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[foo]
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offsetExists(foo)
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offsetGet(foo)
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[bar]
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offsetExists(bar)
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offsetSet(bar,foo)
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[null]
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offsetExists(null)
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offsetGet(null)
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offsetSet(null,baz)
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[foo][bar]
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offsetExists(foo)
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offsetGet(foo)
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offsetExists(bar)
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offsetGet(foo)
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offsetSet(bar,abc)
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[foo][bar]
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offsetExists(foo)
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offsetGet(foo)
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offsetExists(bar)
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offsetGet(bar)

‎Zend/tests/assign_coalesce_004.phpt

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--TEST--
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Coalesce assign (??=): Non-writable variable
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--FILE--
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<?php
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function foo() { return 123; }
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foo() ??= 456;
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?>
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--EXPECTF--
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Fatal error: Can't use function return value in write context in %s on line %d

‎Zend/tests/assign_coalesce_005.phpt

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--TEST--
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Coalesce assign (??=): Cannot reassign $this
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--FILE--
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<?php
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class Test {
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public function foobar() {
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$this ??= 123;
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}
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}
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?>
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--EXPECTF--
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Fatal error: Cannot re-assign $this in %s on line %d

‎Zend/zend_ast.c

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@@ -1672,6 +1672,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
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EMPTY_SWITCH_DEFAULT_CASE();
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}
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break;
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case ZEND_AST_ASSIGN_COALESCE: BINARY_OP(" \?\?= ", 90, 91, 90);
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case ZEND_AST_BINARY_OP:
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switch (ast->attr) {
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case ZEND_ADD: BINARY_OP(" + ", 200, 200, 201);

‎Zend/zend_ast.h

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@@ -120,6 +120,7 @@ enum _zend_ast_kind {
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ZEND_AST_INSTANCEOF,
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ZEND_AST_YIELD,
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ZEND_AST_COALESCE,
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ZEND_AST_ASSIGN_COALESCE,
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ZEND_AST_STATIC,
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ZEND_AST_WHILE,

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