How to make work variable inside curl function (PHP)

I need to pass the data from varlable saved1 into reply_message (line 45) and it doesn’t work

I’ve tried " {"text": "${saved1}"} but nothing response.

the result expected are "text": "line1 \n 123 \n line 3"

Output

line 1

123

line 3

Any help are appreciate
Thanks & Regards

<?php
    send_reply($access_token,$reply_message);
        
    
        $reply_message='{
            
            "messaging_type": "RESPONSE",
            "recipient": {
                "id": "1631126643573991"
                },
            "message": {
                "text": "line1 \n $saved1 \n line 3"                
                }
        }';
        
    send_reply($access_token,$reply_message);
    }
    

    function send_reply($access_token='',$reply='')
    {
        $url="https://graph.facebook.com/v14.0/me/messages?access_token=$access_token";
        $ch = curl_init();
        $headers = array("Content-type: application/json");
        curl_setopt($ch, CURLOPT_URL,$url);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_POST,1);
        curl_setopt($ch, CURLOPT_POSTFIELDS,$reply);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $st=curl_exec($ch);
        $result=json_decode($st,TRUE);
        return $result;
    }

?>

>Solution :

Use concatenation for $saved1 like below.

$reply_message='{

            "messaging_type": "RESPONSE",
            "recipient": {
                "id": "1631126643573991"
                },
            "message": {
                "text": "line1 \n '.$saved1.' \n line 3"
                }
        }';