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<?php //var_dump(get_defined_constants(true)['Core']); class Foo { const ERR_SOME_CONST = 6001; const ERR_SOME_OTHER_CONST = 5001; function bar() { $x = 6001; $fooClass = new ReflectionClass ( 'Foo' ); $constants = $fooClass->getConstants(); $constants = get_defined_constants(true)['user']; var_dump($constants); $constName = null; foreach ( $constants as $name => $value ) { if ( $value == $x ) { $constName = $name; break; } } echo $constName; } } echo (new Foo)->bar();

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