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GhostFieldAccessTrait.php
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GhostFieldAccessTrait.php
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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
namespace Wikimedia\Reflection;
/**
* Trait for accessing "ghost fields".
*
* Ghost fields are fields that have been created in an object instance
* by PHP's unserialize() mechanism, though they no longer exist
* in the current version of the corresponding class.
*
* Accessing non-public ghost fields offers some challenges due to
* how they are handled by PHP internally.
*
* @see https://www.php.net/manual/en/language.types.array.php#language.types.array.casting
* @since 1.36
*/
trait GhostFieldAccessTrait {
/**
* Get the value of the ghost field named $name,
* or null if the field does not exist.
*
* @param string $name
* @param class-string ...$aliases
* @return mixed|null
*/
private function getGhostFieldValue( string $name, string ...$aliases ) {
if ( isset( $this->$name ) ) {
return $this->$name;
}
$data = (array)$this;
// Protected variables have a '*' prepended to the variable name.
// These prepended values have null bytes on either side.
$protectedName = "\x00*\x00{$name}";
if ( isset( $data[$protectedName] ) ) {
return $data[$protectedName];
}
// Private variables have the class name prepended to the variable name.
// These prepended values have null bytes on either side.
$thisClass = get_class( $this );
$privateName = "\x00{$thisClass}\x00{$name}";
if ( isset( $data[$privateName] ) ) {
return $data[$privateName];
}
// Check old aliased class names as well.
foreach ( $aliases as $thisClass ) {
$privateName = "\x00{$thisClass}\x00{$name}";
if ( isset( $data[$privateName] ) ) {
return $data[$privateName];
}
}
return null;
}
/**
* In PHP <= 8.1, private fields of a class are not properly restored
* when the class is aliased to a new name, since the private fields are
* prefixed with the *old* name of the class. This method can be used
* to restore them if present after deserialization.
*
* @param string $name
* @param class-string ...$aliases
*/
private function restoreAliasedGhostField( string $name, string ...$aliases ): void {
$data = (array)$this;
foreach ( $aliases as $thisClass ) {
$privateName = "\x00{$thisClass}\x00{$name}";
if ( isset( $data[$privateName] ) ) {
$this->$name = $data[$privateName];
unset( $data[$privateName] );
return;
}
}
}
}

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GhostFieldAccessTrait.php (3 KB)

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