PHP has four different variable scopes: static, parameter, global, local.
1. Global variables
are in All variables defined outside the function have global scope, and variables declared inside the function are local variables and can only be accessed within the function. To use global variables in a function, use the global keyword.
Another important feature of variable scope is static variable (staticvariable). Static variables only exist in the local function scope, but their values are not lost when program execution leaves this scope.
Static variables defined in a function cannot be called outside the function.
Static variables also provide a way to deal with recursive functions. A recursive function is a function that calls itself. Be careful when writing recursive functions, as they may recurse indefinitely. You must ensure that there are adequate means to terminate recursion.
<?php
function Test()
{
static $count = 0;
$count++;
echo $count;
if ($count < 10) {
Test ();
}
$count--;
}
?>
Copy after login
3. Local variables
Parameters are local variables that pass values to the function through the calling code.
4. Variable variables
Sometimes it is very convenient to use variable variable names. That is, the variable name of a variable can be set and used dynamically. An ordinary variable is set by declaration, for example:
# #At this time, both variables are defined: the content of
$a is "hello" and the content of
$hello
is "world". Therefore, it can be expressed as:
##
echo <span style="color:#000000;">"$a ${$a}"<span style="color:#0000BB;"></span>;<span style="color:#007700;"></span>?><span style="color:#DD0000;"></span><span style="color:#007700;"></span><span style="color:#0000BB;"></span></span>The following way of writing is more accurate And the same result will be output:
The above is the detailed content of Example analysis of variables and constants in PHP. For more information, please follow other related articles on the PHP Chinese website!
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
PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals.
This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase.
What is a vowel?
Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase:
a, e, i, o, u
Example 1
Input: String = "Tutorialspoint"
Output: 6
explain
The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.
PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7
