Index: src/wp-includes/compat.php
===================================================================
--- src/wp-includes/compat.php	(revision 45454)
+++ src/wp-includes/compat.php	(working copy)
@@ -510,7 +510,7 @@
 	require_once ABSPATH . WPINC . '/spl-autoload-compat.php';
 }
 
-if ( ! function_exists( 'is_countable' ) ) {
+if ( ( version_compare( PHP_VERSION, '7.3' ) > 0 ) && ! function_exists( 'is_countable' ) ) {
 	/**
 	 * Polyfill for is_countable() function added in PHP 7.3.
 	 *
@@ -532,7 +532,7 @@
 	}
 }
 
-if ( ! function_exists( 'is_iterable' ) ) {
+if ( ( version_compare( PHP_VERSION, '7.3' ) > 0 ) && ! function_exists( 'is_iterable' ) ) {
 	/**
 	 * Polyfill for is_iterable() function added in PHP 7.1.
 	 *