The difference and usage of single and double quotes in php

In PHP, the difference between single and double quotes lies in the way of string parsing: single quotes do not parse variables, output literals, do not process escape sequences, and cannot represent single quotes; double quotes parse variables and handle escapes Sequence, can represent double quotes. When single quotes are selected, they are used to output literal strings to avoid misuse of single quote terminators; when double quotes are selected, they are used to parse variables, use escape sequences or special characters, or nested double quotes include single quotes.

The difference and usage of single and double quotes in PHP

The difference between single and double quotes in PHP lies in the string Different parsing methods affect the processing of variables, escape sequences and special characters.

1. Variable parsing

• Single quotation marks ('): Do not parse variables and output literals directly.
• Double quotes ("): Parse the variable and insert its value into the string.

2. Escape sequence

• Single quotes: Do not process escape sequences and output them literally.
• Double quotes: Process escape sequences and convert them into special characters.

##3 . Special characters

##Single quotation mark: cannot represent single quotation mark, need to use escape character \.

• Double quotation mark: can represent double quotation mark, no need to escape ##.
• #When to use single quotes

When you need to output a literal string without variables or special characters

When Need to avoid misuse of single quotes as string terminators
• When to use double quotes

When you need to parse a variable and insert it. When the string contains escape sequences or special characters,

When the string contains single quotes, nested double quotes are required.
• ##Example

• $name = 'John Doe';
  
  // 输出 "John Doe"
  echo "$name";
  
  // 输出 'John Doe'
  echo '$name';
  
  // 输出 "John Doe is here"
  echo "$name is here";
  
  // 输出 "Apostrophe is written as '"
  echo "Apostrophe is written as '\"";

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