Home > Backend Development > PHP Tutorial > PHP general knowledge review: custom functions and internal functions

PHP general knowledge review: custom functions and internal functions

little bottle
Release: 2023-04-05 21:10:01
forward
2833 people have browsed it

1. Variable scope and static variables

Function parameters and parameter reference transfer

Function return Value and reference returns

Import of external files

Inspection of system built-in functions

Variables The scope of a variable is also called the scope of a variable. The scope of a variable is the context in which it is defined (also the scope in which it takes effect). Most PHP variables have only one valid scope, and this single scope also includes files introduced by include and require.

global keyword

$GLOBALS and other super-global arrays

Static variables are only in Exists in the local function scope, and its value will not disappear when the program execution leaves the scope.

static keyword

1. Only initialize once

2. Assignment is required during initialization

3. The value will be retained every time the function is executed

4. The modified function is local and is only saved inside the function

  5. The number of function calls can be recorded to terminate the recursion under certain conditions


function myFunc(){
static $a = 1;
echo $a++;
}
myFunc();        //1
myFunc();        //2
myFunc();        //3
Copy after login


<?php
$count = 5;
function getCount(){
static $count;
return $count++;
}
echo $count;        //5
$count++;


echo getCount();    //null
echo getCount();    //1 null + 1 = 1
?>
Copy after login

Functions are passed by value by default, if you want the function to modify its value, you must pass it by reference.

<?php
$a = 1;
function myFun(&$a){
$a = 100;
}
myFun($a);
echo $a;        //100
?>
Copy after login

2. The return value of the function

The value is returned through the optional return statement

Any type including an array or object can be returned

The return statement will terminate the execution of the function and return control to the control point of the function

If return is omitted, the return value is null

It is impossible to have multiple return values

To return a reference from a function, you must use the reference operator when declaring the function and assigning the return value to a variable. Import of external files

include/reqlude Difference warning/fatal error include_once/reqlude_once

3. System built-in functions

Time and date: date(), strtottime(), time(), miketime(), microtime(), date_default_timezone_set()

IP processing function: iptolong(), longtoip()

Print processing: print(), printf(), print_r(), echo, sprintf(), var_dump() , var_export()

Serialization and deserialization functions: serialize(), unserialize() https://www.cnblogs.com/yamtsin/p/5922872.html

String Processing function: implod()

Problem-solving method:

Focus on memorizing the relevant content of the PHP function definition, understand the variable scope, static variables, function parameters, and return values, focus on memorizing the relevant content Built-in function for summarization.

If you want to know more, please go to

PHP video tutorial

to learn more!

The above is the detailed content of PHP general knowledge review: custom functions and internal functions. For more information, please follow other related articles on the PHP Chinese website!

Related labels:
source:cnblogs.com
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Latest Articles by Author
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template