This article mainly introduces the common character functions in PHP, and summarizes and analyzes the common character functions substr, preg_match, strpos, dirname and str_split in PHP in the form of examples. The functions, usage and related Notes, friends in need You can refer to the following examples
This article summarizes common character functions in PHP. Share it with everyone for your reference, the details are as follows:
1. string substr(string $string, int $start [,int $length])
Function function: Return the substring of the string string specified by the start and length parameters.
Parameters:
string: Enter the character string.
start: If start is a non-negative number, the returned string will start from the start position of string and start counting from 0. For example, in 'abcdef', position 0 is 'a' and position 2 is 'c ';
If start is a negative number, the returned string will start from the start character forward from the end of the string.
If the length of string is less than or equal to start, return FALSE.
$rest=substr(" abcdef ",-1);//返回“ f ” $rest=substr(" abcdef ",-2);// 返回 “ ef ” $rest=substr(" abcdef ",-3,1); //返回 “ d ”
$length: If a positive length is provided, the returned string will contain at most length characters from start (depending on the length of the string).
If a negative length is provided, many characters at the end of the string will be missed, that is, characters will not be considered from the end (you can understand that I truncate). If start is not in the text, then a will be returned Empty string.
If length is provided with a value of 0, FALSE or NULL, an empty string will be returned.
If length is not provided, the returned string will be from the start position to the end of the character.
$rest=substr("abcdef","0","-1"); //返回 abcde $rest=substr("abcdef","2","-1"); //返回 cde $rest=substr("abcdef"," 4","-4"); //返回 NULL $rest=substr("abcdef","-3","-1"); //返回 de
[ ] The square brackets indicate that the parameter is optional. If not set, it will be the default parameter. (I have been working with PHP for almost 8 months, and I have always wondered why function parameters need to be enclosed in square brackets. Today I finally couldn’t help but Baidu! Shame!)
2. int preg_match(string $pattern, string $subject [, array &$matches [, int $flag=0 [, int $offset=0 ]]])
Function : Search for a match between subject and the regular expression given by pattern.
Parameters:
$pattern: Pattern to be searched, Character type.
$subject: Input string.
$matches: If the parameter matches is provided, it will be populated as the search results, $matches[0] contains the text matched by the complete pattern, $matches[1] will contain the first capture Subgroups match text, and so on.
$flags :flags can be set to the following tag values:
PREG_OFFSET_CAPTURE
If this flag is passed, for each occurrence Matches are returned with the string offset (relative to the target string) appended. Note: This will change the array populated in the matches argument so that each element becomes a string whose 0th element is the matched string. , the first element is the offset of the matching string in the target string subject.
offset:
Usually, the search starts from the beginning of the target string Unknown start. The optional parameter offset is used to specify the search starting from an unknown point in the target string (unit is byte).
Note:
Use the offset parameter It is different from passing to preg_match() the result of intercepting the target string according to the position through substr($subject, $offset), because pattern can contain assertions such as ^,$ or (?
<?php $subject = "abcdef"; $pattern = '/^def/'; preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3); print_r($matches); ?>
The above routine will output:
Array ( )
<?php $subject = "abcdef"; $pattern = '/^def/'; preg_match($pattern, substr($subject,3), $matches, PREG_OFFSET_CAPTURE); print_r($matches); ?>
will produce a match
Array ( [0] => Array ( [0] => def [1] => 0 ) )
3. strpos(string,find,start)
string: Required, specifies the string to be searched.
find: Required, specifies the characters to be found.
start: Optional, specifies the position to start the search, starting from the first character by default.
This function is case-sensitive. If you do not want this, you can use the stripos() function
Example:
echo strpos("Hello world! "," wo ");// 输出 6
4. string dirname(string path)
Function: Get the directory name in the path. In Win32 systems, you can use slashes (/) or backslashes (\); but in other operating systems, the paths are (/).
$path = "/etc/hostname"; $file = dirname($path);
$file is "/etc"
5. str_split(string,length)
string 必需。规定要分割的字符串。
length 可选。规定每个数组元素的长度。默认是 1。
<?php print_r(str_split("Hello")); ?>
运行结果:
Array ( [0] => H [1] => e [2] => l [3] => l [4] => o )
The above is the detailed content of Summary of commonly used character functions in php. For more information, please follow other related articles on the PHP Chinese website!

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

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 originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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

SublimeText3 English version
Recommended: Win version, supports code prompts!

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Mac version
God-level code editing software (SublimeText3)

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Atom editor mac version download
The most popular open source editor