Update PHP version requirement to >=7.2.0

Author: donatj

README.md

@@ -9,7 +9,7 @@ A collection of global `array_*` functions appending to the native PHP set.
 
 ## Requirements
 
-- **php**: >=5.3.0
+- **php**: >=7.2.0
 
 ## Installing
 
@@ -105,4 +105,4 @@ function array_key_refill(array $array, array $keys [, $fill = array()])
 
 - ***array***
 
-Given a keyed array, fills any missing values.
+Given a keyed array, fills any missing values.