php - PHP 查询中的左大括号和大括号是什么意思？

Question

这个问题已经有答案了:

Curly braces in string in PHP (4 个回答)

Reference Guide: What does this symbol mean in PHP? (PHP Syntax) (25 个回答)

已关闭 4 年前。

我遇到了一个程序，其中查询以不同的方式形成，如下所示:

$insert_query = "INSERT INTO projects(project_user_id, project_name, project_body) ";
$insert_query .= "VALUES({project_user_id}, '{$project_name}', '{$project_body});

我知道第二行旨在将其与第一行连接起来，以提高查询的可读性。但让我烦恼的是左大括号和右大括号有什么用？仅仅是为了提高代码的可读性还是相反？

Answer 1

来自PHP Documentation :

Complex (curly) syntax

This isn't called complex because the syntax is complex, but because it allows for the use of complex expressions.

Any scalar variable, array element or object property with a string representation can be included via this syntax. Simply write the expression the same way as it would appear outside the string, and then wrap it in { and }. Since { can not be escaped, this syntax will only be recognised when the $ immediately follows the {.