使用 php 在字符串中打印变量

print variable in string using php

我尝试用 php 变量替换短代码并尝试在字符串中打印变量值。希望下面的代码会给你更多 idea.below 是我的代码:

<?php
$string='hi i am [name] suthar and my email is [mail]. today i very happy because [message]';
$name="xyz";
$mail="xyz@xyz.com";
$message="my message"; 
$string=str_replace('[name]', '$name', $string ); 
$string=str_replace('[mail]', '$mail', $string ); 
$string=str_replace('[message]', '$message', $string ); 
echo $string; 
?>

我想要的输出:

hi i am xyz suthar and my email is xyz@xyz.com. today i very happy because my message.

$string='hi i am [name] suthar and my email is [mail]. today i very happy because [message]';
$name="xyz";
$mail="xyz@xyz.com";
$message="my message"; 
$string=str_replace('[name]', $name, $string ); 
$string=str_replace('[mail]', $mail, $string ); 
$string=str_replace('[message]', $message, $string ); 
echo $string; 

为什么变量需要单引号?