The usage of "reference &". When should I use it and when should I solve the problem?

Usage of & quot; reference & amp; & quot. the usage of & quot; reference & amp; & quot. when it is used, when it should not be used, and if it is unclear, Zend will be optimized. it is generally used when the variables are referenced and the characters are connected to the (character) variables ., if the value of the passed variable is used, you need to change the usage of "reference. when should I use it? When should I not?
Usage of "reference &". When should I use it and when should I not?

------ Solution --------------------
Don't use it unless you know it. Zend will optimize it.
------ Solution --------------------
It is generally used when a variable is referenced and the character is connected with the (character) variable.
------ Solution --------------------
If the value of the passed variable needs to be changed during your use, you can write it like this!
$ Aaa = 0
Open (& $ aaa)
{
$ Aaa = 1;
}
This is probably the case!
------ Solution --------------------
Very troublesome. learning...
------ Solution --------------------
Read the manual, this requirement is not high, and the zend Engine of php will be optimized.
------ Solution --------------------
C language.
------ Solution --------------------
Check the replacement of variables in C.