Reflection: show the name of object constants used as default properties

When a property default is based on a global constant, identify and use the
name of that constant. Previously, `format_default_value()` assumed that
non-scalar and non-array defaults were always going to be `IS_CONSTANT_AST`
pointers, and when the AST expression had been evaluated and produced an
object, depending on when the `ReflectionClass` or `ReflectionProperty`
instance had been created, the default was shown as one of `callable`,
`__CLASS__`, or `...`.

Instead, if the default value is an object (`IS_OBJECT`), find the name of the
`zend_constant` in the global `EG(zend_constants)` that points to the same
value, and show that name. If no constant is found, instead of the confusing
output of treating the object as an `IS_CONSTANT_AST` value, show
`"<Unknown object value>"`.

Add test cases for each of the `callable`, `__CLASS__`, and `...` cases to
confirm that they all now properly show the name of the constant.

Closes phpgh-15902

ext/reflection/php_reflection.c

@@ -682,6 +682,26 @@ static int format_default_value(smart_str *str, zval *value) {
 			format_default_value(str, zv);
 		} ZEND_HASH_FOREACH_END();
 		smart_str_appendc(str, ']');
+	} else if (Z_TYPE_P(value) == IS_OBJECT) {
+		// Look through the global constants, GH-15902
+		zend_constant *constant;
+		zend_string *name = NULL;
+
+		ZEND_HASH_MAP_FOREACH_PTR(EG(zend_constants), constant) {
+			if (
+				Z_TYPE(constant->value) == IS_OBJECT &&
+				Z_OBJ(constant->value) == Z_OBJ_P(value)
+			) {
+				// Found the right constant
+				name = constant->name;
+				break;
+			}
+		} ZEND_HASH_FOREACH_END();
+		if (name == NULL) {
+			smart_str_appends(str, "<Unknown object value>");
+		} else {
+			smart_str_append(str, name);
+		}
 	} else {
 		ZEND_ASSERT(Z_TYPE_P(value) == IS_CONSTANT_AST);
 		zend_string *ast_str = zend_ast_export("", Z_ASTVAL_P(value), "");

ext/reflection/tests/gh15902/ReflectionClass-callable.phpt

@@ -0,0 +1,36 @@
+--TEST--
+ReflectionClass object default property - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionClass(C::class);
+var_dump( (string)$reflector );
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-callable.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = FOO ]
+  }
+
+  - Methods [0] {
+  }
+}
+"

ext/reflection/tests/gh15902/ReflectionClass-class.phpt

@@ -0,0 +1,37 @@
+--TEST--
+ReflectionClass object default property - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionClass(C::class);
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-class.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = FOO ]
+  }
+
+  - Methods [0] {
+  }
+}
+"

ext/reflection/tests/gh15902/ReflectionClass-dots.phpt

@@ -0,0 +1,39 @@
+--TEST--
+ReflectionClass object default property - used to say "..."
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionClass(C::class);
+$c = $reflector->newLazyGhost(function () {});
+
+define('FOO', new stdClass);
+
+$c->a;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-dots.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = FOO ]
+  }
+
+  - Methods [0] {
+  }
+}
+"

ext/reflection/tests/gh15902/ReflectionProperty-callable.phpt

@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionProperty(C::class, 'a');
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = FOO ]
+"

ext/reflection/tests/gh15902/ReflectionProperty-class.phpt

@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionProperty(C::class, 'a');
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = FOO ]
+"

ext/reflection/tests/gh15902/ReflectionProperty-dots.phpt

@@ -0,0 +1,22 @@
+--TEST--
+ReflectionProperty object default - used to say "..."
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionProperty(C::class, 'a');
+$lazyFactory = new ReflectionClass(C::class);
+$c = $lazyFactory->newLazyGhost(function () {});
+
+define('FOO', new stdClass);
+
+$c->a;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = FOO ]
+"