What are the beginnings of php strings?

php strings start with single quotes, double quotes, Heredoc syntax, Nowdoc syntax, backslash, NULL literal, etc. Detailed introduction: 1. Single quotes, the beginning of the string can also be represented by single quotes, such as 'Hello World'; 2. Double quotes, the beginning of the string can also be represented by double quotes, such as "Hello World"; 3. Heredoc syntax , can be used to represent a string that starts with <<< followed by an identifier and ends with the identifier; 4. Nowdoc syntax, etc.

The operating environment of this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

There are the following situations at the beginning of a PHP string:

1. Single quotes: The beginning of a string can be represented by single quotes. For example: 'Hello World'.

2. Double quotes: The beginning of a string can also be represented by double quotes. For example: "Hello World".

3. Heredoc syntax: Heredoc syntax can also be used to represent a string, which starts with <<< followed by an identifier and ends with the identifier. For example:

   ```
   $str = <<<EOT
   Hello World
   EOT;
   ```

4. Nowdoc syntax: Similar to Heredoc syntax, Nowdoc syntax is used to represent plain text strings. It also starts with <<< followed by an identifier and ends with character, but Nowdoc does not support variable parsing. For example:

   ```
   $str = <<<&#39;EOT&#39;
   Hello World
   EOT;
   ```

5. Backslash: You can use backslash at the beginning of the string to escape special characters. For example: \n represents a newline character, \t represents a tab character, etc.

6. NULL literal: NULL literal can be used at the beginning of a string to represent an empty string. For example: $str = NULL.

PHP's string starting method is not limited to the above situations, but can also be spliced ​​to generate strings through various operators, functions and methods. For example, use the concatenation operator "." to connect strings together, use string functions such as substr(), str_replace(), etc. to process strings, or use object methods to obtain strings.

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