PHP pass and receive parameters in function Body _php tutorial

In PHP functions, parameter passing can be divided into two types: value passing and reference passing (also known as address passing).

By default, PHP passes parameters by value. A value-passing parameter invokes a function to pass a constant or a variable's value (often referred to as an argument) to a function's argument (often called a formal parameter). The characteristic of value passing is that the actual participating row parameters are stored in memory separately, and are two unrelated independent variables. Therefore, when you change the value of a parameter inside a function, the value of the argument is generally not changed.

A reference pass (passed by address) is characterized by the fact that the participating row parameter shares a piece of memory. Therefore, when the value of the parameter changes, the value of the argument is changed accordingly. From this perspective, it can be assumed that a participating argument is the same variable.

When you define a reference pass parameter, you can precede the argument with a reference symbol &.

 
  Program output: Test characters! Print complete

PHP also supports variable-length parameter lists. When a function is defined, no parameters are specified. When calling a function, you can specify the number of parameters as needed, and obtain the parameter information through several system functions related to the parameter. Specific instructions are:

 
  Program output: function contains: 4 parameter parameters The accumulator tray is: 10

Func_num_args function Function: Returns the number of arguments passed to the function, with the following syntax: int func_num_args (void). Description: Returns the number of arguments passed to the currently defined function. If you call this function from outside the function definition, func_get_arg () will produce a warning.

Func_num_args () can be used to combine Func_get_arg () and Func_get_args () to allow a user-defined function to accept the Variable-length parameter list. where Func_get_arg () returns the item from the argument list, whose syntax: int func_get_arg (int arg_num), passes back the Arg_num parameter of the parameter list that defines the function, whose arguments start with 0. and calling this function outside the function definition generates a warning, and when Arg_num is greater than the number of arguments actually passed by the function, it also generates a warning and returns false.

The difference between the Func_get_args () function and the Func_get_arg () function is that the Func_get_args () function returns an array whose elements correspond to the number of parameter columns of the current consumer-defined function.

When we build PHP classes, flexible use of these three functions, can play a very good effect, such as outside in the creation of PHP and MySQL link class, you can write the following code:

 
  0) {$args =func_get_args (); $this->host= $args [0]; $this->user= $args [1]; $this->pass= $args [2]; $this Connect ();}}? >

A sample program is given:

 
  n "; if ($numargs >= 2) {echo" Second argument is: ". Func_get_arg (1). "
n ";} $arg _list = Func_get_args (); for ($i = 0; $i < $numargs; $i + +) {echo "Argument $i is:". $arg _list[$i]. "
n ";}} Foo (1, 2, 3); >

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