Detailed example explanation: PHP commonly used string functions

String operations in PHP are one of the most common operations. Making good use of string functions can improve code efficiency and simplify development work. In this article, I will lead you to understand the commonly used string functions in PHP, including basic string operation functions and regular expression functions.

1. String length and interception

1. strlen() function

strlen() function is used to obtain the length of a string, such as:

$str = "hello world";
echo strlen($str);   // 输出 11

2. mb_strlen() Function

mb_strlen() functions similarly to strlen(), but is designed for multi-byte character sets. When a character set contains multi-byte characters, there will be problems using the strlen() function to calculate the string length.

$str = "你好，世界";
echo mb_strlen($str);   // 输出 6

3. substr() function

substr() function can be used to intercept part of a string. Two parameters can be passed, the first one is the character to be intercepted. string, the second parameter is the starting position, and the third parameter is the intercepted length.

$str = "hello world";
echo substr($str, 2, 5);  // 输出 llo w

2. String search, replacement and splitting

1. strpos() function

strpos() function is used to find a string in another string The position of the first occurrence in a string. If the string does not exist, returns false.

$str = "hello world";
echo strpos($str, "world");  // 输出 6

2. str_replace() function

str_replace() function is used to replace some characters in the string and accepts three parameters: the character to be replaced, and the characters and the string to replace within.

$str = "hello world";
echo str_replace("world", "php", $str);  // 输出 hello php

3. explode() function

explode() function is used to split the string according to the specified delimiter and return an array.

$str = "hello world";
$arr = explode(" ", $str);
print_r($arr);  // 输出 Array([0] => hello [1] => world)

3. String formatting

1. strtolower() function

strtolower() function is used to convert English characters in a string to Lowercase and returns the converted string.

$str = "Hello World";
echo strtolower($str);  // 输出 hello world

2. strtoupper() Function

strtoupper() function is used to convert English characters in a string to uppercase and return the converted string.

$str = "Hello World";
echo strtoupper($str);  // 输出 HELLO WORLD

3. ucwords() function

ucwords() function is used to convert the first English letter in the string to uppercase and return the converted string .

$str = "hello world";
echo ucwords($str);  // 输出 Hello World

4. Regular expressions

1. preg_match() function

preg_match() function is used to match regular expressions and return matching results .

$str = "hello world";
if (preg_match("/world/", $str)) {
    echo "匹配成功";
} else {
    echo "匹配失败";
}

2. preg_replace() Function

preg_replace() function is used to search and replace strings with regular expressions.

$str = "hello world";
echo preg_replace("/world/", "php", $str);  // 输出 hello php

The above are the string functions and regular expression functions commonly used in PHP. Mastering the basic usage of these functions will help you get twice the result with half the effort when manipulating strings and improve coding efficiency.

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