The use of the "&" operator when declaring a function, when modifying a parameter

/*

• Function Name: Test
• Parameter delivery Method: "&" means reference delivery
• Parameters: $a
  */
  Function test (& $a) {
  $a + = 1;
  }

Declare variable B, and assign a value of 1
$b = 1;

The value of print variable B is 1
Var_dump ($b);

Call the test function
Test ($b);

The value of print variable B is 2
Var_dump ($b);

Note: When declaring the test function, the passed arguments are passed with the reference "&" instead of the value pass, and the value is passed without the "&" operator, so the result of the calculation in the body of the function affects the arguments passed in, and when the test function is called, the pass parameter is B, After the calculation of the test function, the result of the final print is 2, not the 1 declared above.

The use of the "&" operator when declaring a function, when modifying a parameter