Require PHP version >=8.0, Ruby >=2.7, and Python >=3.8

If you are running an older version of PHP, you can install a previous release
of the protobuf PHP extension by running pecl install protobuf-3.23.3.

PiperOrigin-RevId: 546056449

php/composer.json

diff --git a/php/composer.json b/php/composer.json
index 0e498fc..c00d686 100644
--- a/php/composer.json
+++ b/php/composer.json
@@ -6,7 +6,7 @@
   "homepage": "https://developers.google.com/protocol-buffers/",
   "license": "BSD-3-Clause",
   "require": {
-    "php": ">=7.0.0"
+    "php": ">=8.0.0"
   },
   "require-dev": {
     "phpunit/phpunit": ">=5.0.0 <8.5.27"