PHP Quote's Call

Invocation of PHP Reference
1.function Test ($arr) {}
echo Test (& $arr);
2.function Test (& $arr) {}
echo Test ($arr);
1 and 2 are the same effect.

3.function &test ($arr) {return $result;}
echo &test ($a); effective
echo test ($a); Returns a value, not a reference
Summary: The reference is returned only when the method is defined with the & and the method in front of the method name plus & when it is called.

4. $a = $b;
When $ A and $b are not re-assigned, that is, when a write operation occurs, the same as the $a=& $b, which is equivalent to an assignment reference.
Copies a copy of a value of $ A only when a $ A or $b change occurs

