Online PHP editor | output for 1bFUF

<?php $obj = new stdClass; $obj->{'123'} = '456'; // defined property but unusable as obj->property; see below. print_r($obj); echo 'Via {\'123\'}: ' . $obj->{'123'},"\n"; if (isset($obj->{'123'})) { echo '123 is set',"\n";} if (property_exists($obj,'123')) echo 'property 123 exists',"\n"; echo $obj->123; // Parse error: ...unexpected '123' (T_LNUMBER), expecting identifier (T_STRING) or variable (T_VARIABLE) or '{' or '$' $obj->{'a123'} = $obj->{'123'}; print_r($obj); echo 'Via Property a123: ' . $obj->a123,"\n"; // making a hash out of property a $obj->a["123"] = $obj->{'123'}; $obj->a["a123"] = $obj->{'a123'}; var_dump($obj); echo 'Via Property "a" and hashkey "123": ' . $obj->a["123"],"\n"; // contrast: $obj = (object)array('123' => '456'); // property 123 is invalid print_r($obj); echo $obj->{'123'},"\n"; // so "Undefined property: stdClass::$123"