PHP quote trap

PHP reference Trap 1. & nbsp; $ a333; & nbsp; $ c & amp; $ a; & nbsp; $ d888; & nbsp; & nbsp; $ c & amp; $ d; & nbsp; echo $ c; & nbsp; echo $ a PHP reference trap
1. $ a = '000000 ';
$ C = & $;
$ D = '000000 ';
$ C = & $ d;
Echo $ c;
Echo $;

2. $ a = '000000 ';
$ C = & $;
$ D = '000000 ';
$ C = $ d;
Echo $ c;
Echo $;

In the fourth row, $ c = $ d and $ c = & $ d lead to completely different results.
$ C = $ d. Because $ c is a reference of $ a, the values of $ c and $ a will change to 888,
However, $ c = & $ d indicates that $ c has changed to a reference of $ d. It has nothing to do with $ a. Therefore, the value of $ a is still 333.
Note that referencing is just an alias, not a pointer.
In fact, it is similar to a Unix hard connection.
Http://www.php.net/manual/zh/language.references.whatare.php