How to pass parameters to php function

Function parameter passing in php has formal parameter passing (borrowing the term from programming languages ​​such as c language).

That is, assigning the value of the variable to the parameter of the function. All operations performed on the function parameter have nothing to do with the original variable.

//php
function testX( $b )
{
     return $b-=2;
}
$a = 5 ;
$c = testX($a);
print_r($a);//5
print_r($c);//3

And address transfer (reference transfer) is to give the address of the variable to the parameter of the function. All operations performed on the parameters in the function are equivalent to operations on the variables.

//php
function testS( &$b )
{
     return $b-=2;
}
$a = 5 ;
$c = testX($a);
print_r($a);//3
print_r($c);//3

In PHP, function parameters and variables will all open up space in the memory, but normal parameter passing assigns values ​​​​to parameters, while reference passing does not, it will put the address of the variable

Go to the space where the parameters are located.

It is particularly noteworthy that the writing method of reference passing has been changed after PHP5. As shown in the above code, change the way PHP is written to the same way as other programming languages. You need to

use & when defining, and you don’t need to use & when calling. It is very different from the previous writing method.

//php以前的写法
function &testS( &$b )
{
 return $b-=2;
}
$c = &testS($a);

Advantages:

Personally, I think this change in writing is to reduce the uniqueness of the php language and move closer to the writing methods of other programming languages. In a sense, it allows programmers who are familiar with other programming languages ​​​​to master PHP faster. From the perspective of code reading and logical understanding, it completely ignores all operations performed on variables within the function. It makes more sense for code abstraction.

Disadvantages:

I think for programmers on the front line of development, this is a crazy change. Especially for those doing secondary development. Secondary developers need to develop on the basis of predecessors. When seeing functions, I am used to distinguishing reference-by-value functions with &. Without this writing method, all functions are the same. If a call to a reference-by-value function is involved, the programmer needs to go inside the function to check the code details. Especially when there is an error in the program. You need to understand in detail all the changes made to variables by the reference-by-value function. And canceling the & to call the reference function means that you need to check all the functions called by the program (because you don't know which function is the reference function), and the workload can be imagined!

There are also global variables (global). This is a direct and fast way to define parameters. Set the parameters to be used by the function as global variables. In this way, operations inside the function directly use the variable itself.

There is no problem in using it in a short program, but this is not an ideal way to define parameters when calling external files!

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