对于PHP4
…这重现了错误：
$foo = 'bar';$foo[0] = 'bar';
对于PHP5
…这重现了错误：
$foo = 'bar';if (is_array($foo['bar'])) echo 'bar-array';if (is_array($foo['bar']['foo'])) echo 'bar-foo-array';if (is_array($foo['bar']['foo']['bar'])) echo 'bar-foo-bar-array';
（实际上来自bugs.php.net）
编辑，
因此，即使是字符串，为什么错误也不会出现在第一个if条件中。
因为PHP是一种非常宽容的编程语言，所以我猜。我将用代码说明我的想法：
$foo = 'bar';// $foo is now equal to "bar"$foo['bar'] = 'foo';// $foo['bar'] doesn't exists - use first index instead (0)// $foo['bar'] is equal to using $foo[0]// $foo['bar'] points to a character so the string "foo" won't fit// $foo['bar'] will instead be set to the first index// of the string/array "foo", i.e 'f'echo $foo['bar'];// output will be "f"echo $foo;// output will be "far"echo $foo['bar']['bar'];// $foo['bar'][0] is equal calling to $foo['bar']['bar']// $foo['bar'] points to a character// characters can not be represented as an array,// so we cannot reach anything at position 0 of a character// --> fatal error
