Introducing how to write PHP strings and related details

PHP is a powerful server-side programming language that works with HTML to implement many dynamic web pages and website functions. When programming in PHP, string is a data type often used by developers. This article will introduce how to write PHP strings and related details.

1. String definition

In PHP, strings can be defined with double quotes (") or single quotes ('). For example:

$str1 = "Hello, World!"; // 双引号定义
$str2 = 'Hi, PHP!'; // 单引号定义

The effect of the two writing methods is the same, both define a string variable. It should be noted that the difference between single quotes and double quotes is that the variables in single quotes will not be parsed, while the variables in double quotes will Is parsed as the value of the variable. For example:

$name = 'Tom';
$str3 = "My name is $name."; // 输出结果：My name is Tom.
$str4 = 'My name is $name.'; // 输出结果：My name is $name.

In $str3, $name is parsed as the value of the variable, but in $str4, $name will not be parsed.

2. String connection

When splicing strings, you can use the . (dot) operator to connect two strings. For example:

$str1 = 'Hello, ';
$str2 = 'PHP!';
$str3 = $str1 . $str2; // 输出结果：Hello, PHP!

It should be noted that, When using the . operator for string concatenation, the two strings must be separated by the . operator, otherwise a syntax error will occur.

3. String length

In PHP, use the strlen function to get the length of a string. For example:

$str = 'Hello, PHP!';
$length = strlen($str); // 输出结果：12

4. substring

In PHP, use the substr function to get a character The substring of the string. For example:

$str = 'Hello, PHP!';
$sub_str = substr($str, 7, 3); // 输出结果：PHP

The first parameter of the substr function is the string to be taken, the second parameter is the starting position to be taken, and the third parameter is the The number of characters taken.

5. Replace string

In PHP, use the str_replace function to replace a certain part of a string with another string. For example:

$str = 'Hello, World!';
$new_str = str_replace('World', 'PHP', $str); // 输出结果：Hello, PHP!

The first parameter of the str_replace function is the string to be replaced, the second parameter is the string to be replaced, and the third parameter is the original string to be replaced.

6. Escape string

In PHP, if you need to include special characters such as quotation marks or slashes in a string, you can use the escape character \ to escape these characters. Escape. For example:

$str1 = 'Tom said, "I love PHP!"'; // 原字符串
$str2 = 'Tom said, "I love PHP\!"'; // 转义后的字符串

It should be noted that when using single quotes to define a string, you can only use backslash\ to escape the single quote ' and the backslash itself, while double quotes " and other special characters do not need to be escaped.

To sum up, operations such as definition, connection, length, substring, replacement and escaping of PHP strings are basic operations commonly used in PHP development. Mastering these basic knowledge will help PHP developers improve programming efficiency and speed up development progress.

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