Ubuntu 14.04 LTS에 PHP 7.4 설치 문제

저는 우분투 14.04와 PHP 7.0을 사용하고 있습니다. PHP를 PHP 7.4로 업데이트해야 합니다. ppa:ondrej/php저장소를 추가했습니다 . 그래도 Unable to locate package php7.4PHP를 업데이트하려고 하면 메시지가 나타납니다.

$ sudo add-apt-repository ppa:ondrej/php
 Co-installable PHP versions: PHP 5.6, PHP 7.x and most requested extensions are included. Only Supported Versions of PHP (http://php.net/supported-versions.php) for Supported Ubuntu Releases (https://wiki.ubuntu.com/Releases) are provided. Don't ask for end-of-life PHP versions or Ubuntu release, they won't be provided.

Debian oldstable and stable packages are provided as well: https://deb.sury.org/#debian-dpa

You can get more information about the packages at https://deb.sury.org

IMPORTANT: The <foo>-backports is now required on older Ubuntu releases.

BUGS&FEATURES: This PPA now has a issue tracker:
https://deb.sury.org/#bug-reporting

CAVEATS:
1. If you are using php-gearman, you need to add ppa:ondrej/pkg-gearman
2. If you are using apache2, you are advised to add ppa:ondrej/apache2
3. If you are using nginx, you are advised to add ppa:ondrej/nginx-mainline
   or ppa:ondrej/nginx

PLEASE READ: If you like my work and want to give me a little motivation, please consider donating regularly: https://donate.sury.org/

WARNING: add-apt-repository is broken with non-UTF-8 locales, see
https://github.com/oerdnj/deb.sury.org/issues/56 for workaround:

# LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php
 More info: https://launchpad.net/~ondrej/+archive/ubuntu/php
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmpayt67sik/secring.gpg' created
gpg: keyring `/tmp/tmpayt67sik/pubring.gpg' created
gpg: requesting key E5267A6C from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpayt67sik/trustdb.gpg: trustdb created
gpg: key E5267A6C: public key "Launchpad PPA for Ondřej Surý" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK

$ sudo apt update
Ign http://ap-southeast-1.ec2.archive.ubuntu.com trusty InRelease
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates InRelease      
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports InRelease    
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty Release.gpg            
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty Release                
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/main Sources   
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/restricted Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/universe Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/multiverse Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/main amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/restricted amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/universe amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/multiverse amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/multiverse Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/restricted Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-updates/universe Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/main Sources 
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/restricted Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/universe Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/multiverse Sources
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/main amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/restricted amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/universe amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/multiverse amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/main Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/multiverse Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/restricted Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty-backports/universe Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/main Sources           
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/restricted Sources     
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/universe Sources       
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/multiverse Sources     
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/main amd64 Packages    
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/restricted amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/multiverse amd64 Packages
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/main Translation-en    
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/multiverse Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/restricted Translation-en
Hit http://ap-southeast-1.ec2.archive.ubuntu.com trusty/universe Translation-en
Ign http://ap-southeast-1.ec2.archive.ubuntu.com trusty/main Translation-en_US 
Ign http://ap-southeast-1.ec2.archive.ubuntu.com trusty/multiverse Translation-en_US
Ign http://ap-southeast-1.ec2.archive.ubuntu.com trusty/restricted Translation-en_US
Ign http://ap-southeast-1.ec2.archive.ubuntu.com trusty/universe Translation-en_US
Hit http://ppa.launchpad.net trusty InRelease                                  
Hit http://security.ubuntu.com trusty-security InRelease                       
Hit http://security.ubuntu.com trusty-security/main Sources                    
Hit http://ppa.launchpad.net trusty/main amd64 Packages           
Hit http://security.ubuntu.com trusty-security/universe Sources
Hit http://ppa.launchpad.net trusty/main Translation-en           
Hit http://security.ubuntu.com trusty-security/main amd64 Packages
Hit http://security.ubuntu.com trusty-security/universe amd64 Packages
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Reading package lists... Done 

$ sudo apt install php7.4
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package php7.4
E: Couldn't find any package by regex 'php7.4'

이 문제의 원인은 무엇이며 Ubuntu 14.04에 PHP 7.4를 설치하는 방법은 무엇입니까?