Increment behavior on strings - PHP easter egg?

Question

$var = \'test_1\';
var_dump(++$var); // string(6) \"test_2\" 

$var2 = \'1_test\';
var_dump(++$var2); // string(6) \"1_tesu\"

$var3 = \'test_z\';
var_dump(++$var3);         


        

Answer 1

Its officially documentated http://php.net/language.operators.increment