Backend Development
PHP Tutorial
Parsing of arrays (generators) that dynamically generate content in PHP
Parsing of arrays (generators) that dynamically generate content in PHP
This article introduces to you the analysis of arrays (generators) of dynamically generated content in PHP. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
Definition:
Generator: "An array of dynamically generated content", which is produced only when the value is used.
Use with: keyword yield foreach
Process:
As a generator method, it is equivalent to defining an array;
Each occurrence of yield in the generator is equivalent to defining the value that appears in an array;
foreach will traverse all the values in the generator The value defined by yield (a defined value (expression)) will only be executed when it is used. Other expressions between the current yield and the previous yield will be executed. Expressions after the current yield will not be executed. );
-
If foreach ends normally (not break), check whether there are other expressions after the last yield in the generator that have not been executed. If so, execute them;
Different from threads, it is not executed in parallel. It just switches execution back and forth between the main business logic and the generator. It only saves space but not time.
Imagine the use scenario:
1. Get the big data file, Read line by line in the generator;
2,? ? ?
Example:
gen.php
1 <?php 2 function gen()
3 {
4 echo '生成器开始执行' . PHP_EOL;
5 for ($i = 0; $i < 5; $i++) {
6 echo '产生数据之前:' . $i . PHP_EOL;
7 yield $i;
8 echo '产生数据之后:' . $i . PHP_EOL;
9 }
10 echo '再来一个数据' . PHP_EOL;
11 yield 5;
12 echo '生成器执行结束' . PHP_EOL;
13 }
14 $gen_func = gen();
15 echo '生成器开始执行了吗？' . PHP_EOL;
16 foreach ($gen_func as $key => $val) {
17 echo '使用数据前' . PHP_EOL;
18 echo '使用数据:' . $val . PHP_EOL;
19 echo '使用数据后' . PHP_EOL;
20 //if ($key >= 4) {
21 //break;
22 //}
23 }Execution result:
php gen.php
Has the generator started executing?
The generator starts executing
Before generating data:0
Before using data
Using data:0
After using data
After generating data:0
Before generating data:1
Before using data
Using data:1
After using data
After generating data:1
Before generating data:2
Before using data
Using data:2
After using data
After generating data:2
Before generating data:3
Before using data
Using data:3
After using data
After generating data:3
Before generating data: 4
Before using data
Using data: 4
After using data
After generating data: 4
Another data
Before using data
Using data: 5
After using the data
The generator execution ends
Interpretation of part of the execution process:
1 and 14 lines do not call the generator gen(), Just defined;
2. After entering the foreach loop, start calling gen();
3. When $val needs a value, remember the current position a and execute the generator;
4. Execute to Where yield is defined, the value is obtained. Remember the current position b and return to position a;
5. Loop steps 3 and 4;
6. The loop ends after executing the last place defined by yield. The remaining part;
7. Remove the comments on lines 20, 21, and 22 and execute, "Use data: 4 After using data", there will be no other output.
Others (only PHP7.1.14 version verified)
1. $data = (yield $value);//YES $data = yield $value;/ /NO
2. You can use yield $key => $val;
3. After PHP7, yield from can call generators, arrays, use return, etc.
(Portal: Available in the PHP manual)
Recommended related articles:
New features of generators in PHP7: generator delegation (yield-from) & return Value (return-value)
Simple analysis of PHP generator Generators
The above is the detailed content of Parsing of arrays (generators) that dynamically generate content in PHP. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1671
14
1428
52
1329
25
1276
29
1256
24
PHP vs. Python: Understanding the Differences
Apr 11, 2025 am 12:15 AM
PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.
PHP: A Key Language for Web Development
Apr 13, 2025 am 12:08 AM
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
PHP and Python: Comparing Two Popular Programming Languages
Apr 14, 2025 am 12:13 AM
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 in Action: Real-World Examples and Applications
Apr 14, 2025 am 12:19 AM
PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.
The Enduring Relevance of PHP: Is It Still Alive?
Apr 14, 2025 am 12:12 AM
PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.
PHP and Python: Different Paradigms Explained
Apr 18, 2025 am 12:26 AM
PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.
PHP vs. Other Languages: A Comparison
Apr 13, 2025 am 12:19 AM
PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.
PHP and Python: Code Examples and Comparison
Apr 15, 2025 am 12:07 AM
PHP and Python have their own advantages and disadvantages, and the choice depends on project needs and personal preferences. 1.PHP is suitable for rapid development and maintenance of large-scale web applications. 2. Python dominates the field of data science and machine learning.
