diff --git a/src/PHP.php b/src/PHP.php
index 1e4746e..3f7c113 100644
--- a/src/PHP.php
+++ b/src/PHP.php
@@ -26,6 +26,19 @@
  */
 class PHP extends EE_Site_Command {
 
+	/**
+	 * Default PHP version for new sites. Single source of truth: this is also
+	 * the version the `latest` image tag resolves to and the 8.x fallback for
+	 * unsupported requests. Change this one constant to move the default.
+	 */
+	const DEFAULT_PHP_VERSION = '8.4';
+
+	/**
+	 * All PHP versions EasyEngine ships images for. Keep in sync with the
+	 * `--php` options list in the create() docblock.
+	 */
+	const SUPPORTED_PHP_VERSIONS = [ '5.6', '7.0', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4', '8.5', 'latest' ];
+
 	/**
 	 * @var string $cache_type Type of caching being used.
 	 */
@@ -83,7 +96,6 @@ public function __construct() {
 	 * [--php=<php-version>]
 	 * : PHP version for site. Currently only supports PHP 5.6, 7.0, 7.2, 7.3, 7.4, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, and latest.
 	 * ---
-	 * default: 8.4
 	 * options:
 	 *	- 5.6
 	 *	- 7.0
@@ -95,7 +107,7 @@ public function __construct() {
 	 *	- 8.2
 	 *	- 8.3
 	 *	- 8.4
-	 *  - 8.5
+	 *	- 8.5
 	 *	- latest
 	 * ---
 	 *
@@ -198,7 +210,7 @@ public function create( $args, $assoc_args ) {
 		$this->site_data['site_fs_path']      = WEBROOT . $this->site_data['site_url'];
 		$this->cache_type                     = \EE\Utils\get_flag_value( $assoc_args, 'cache' );
 		$this->site_data['site_ssl_wildcard'] = \EE\Utils\get_flag_value( $assoc_args, 'wildcard' );
-		$this->site_data['php_version']       = \EE\Utils\get_flag_value( $assoc_args, 'php' );
+		$this->site_data['php_version']       = \EE\Utils\get_flag_value( $assoc_args, 'php', self::DEFAULT_PHP_VERSION );
 		$this->site_data['app_sub_type']      = 'php';
 
 		$this->site_data['site_container_fs_path'] = get_public_dir( $assoc_args );
@@ -230,8 +242,8 @@ public function create( $args, $assoc_args ) {
 		}
 		$this->site_data['alias_domains'] = substr( $this->site_data['alias_domains'], 0, - 1 );
 
-		$supported_php_versions = [ 5.6, 7.0, 7.2, 7.3, 7.4, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 'latest' ];
-		if ( ! in_array( $this->site_data['php_version'], $supported_php_versions ) ) {
+		$supported_php_versions = self::SUPPORTED_PHP_VERSIONS;
+		if ( ! in_array( $this->site_data['php_version'], $supported_php_versions, true ) ) {
 			$old_version = $this->site_data['php_version'];
 			$floor       = (int) floor( $this->site_data['php_version'] );
 			if ( 5 === $floor ) {
@@ -240,7 +252,7 @@ public function create( $args, $assoc_args ) {
 				$this->site_data['php_version'] = 7.4;
 				$old_version                    .= ' yet';
 			} elseif ( 8 === $floor ) {
-				$this->site_data['php_version'] = 8.4;
+				$this->site_data['php_version'] = self::DEFAULT_PHP_VERSION;
 				$old_version                    .= ' yet';
 			} else {
 				EE::error( 'Unsupported PHP version: ' . $this->site_data['php_version'] );
diff --git a/src/Site_PHP_Docker.php b/src/Site_PHP_Docker.php
index 9c9184e..18d2c05 100644
--- a/src/Site_PHP_Docker.php
+++ b/src/Site_PHP_Docker.php
@@ -65,7 +65,7 @@ public function generate_docker_compose_yml( array $filters = [], $volumes ) {
 			$db['networks']     = $network_default;
 		}
 		// PHP configuration.
-		$php_image_key = ( 'latest' === $filters['php_version'] ? 'easyengine/php8.4' : 'easyengine/php' . $filters['php_version'] );
+		$php_image_key = ( 'latest' === $filters['php_version'] ? 'easyengine/php' . PHP::DEFAULT_PHP_VERSION : 'easyengine/php' . $filters['php_version'] );
 
 		$php['service_name'] = [ 'name' => 'php' ];
 		$php['image']        = [ 'name' => $php_image_key . ':' . $img_versions[ $php_image_key ] ];