Fix "Only the first byte will be assigned to the string offset"

Occurs in PHP 8.0

ChangeLog.md

@@ -5,6 +5,9 @@ Networking changelog
 
 ## 10.0.0 / 2020-04-10
 
+* Fixed "Only the first byte will be assigned to the string offset"
+  warning in PHP 8.0
+  (@thekid)
 * Implemented xp-framework/rfc#334: Drop PHP 5.6:
   . **Heads up:** Minimum required PHP version now is PHP 7.0.0
   . Rewrote code base, grouping use statements

src/main/php/peer/net/Inet6Address.class.php

@@ -164,26 +164,21 @@ public function createSubnet($subnetSize) {
     $addr= $this->addr;
 
     for ($i= 15; $i >= $subnetSize / 8; --$i) {
-      $addr[$i]= "\x0";
+      $addr[$i]= "\0";
     }
 
-    if($subnetSize%8 > 0) {
-      $lastNibblePos= (int)($subnetSize/8);
-      $lastByte= ord($addr[$lastNibblePos]) & (0xFF << (8 - $subnetSize % 8));
-      $addr[$lastNibblePos]= pack('i*', $lastByte);
+    if($subnetSize % 8 > 0) {
+      $lastNibblePos= (int)($subnetSize / 8);
+      $addr[$lastNibblePos]= chr(ord($addr[$lastNibblePos]) & (0xFF << (8 - $subnetSize % 8)));
     }
     return new Network(new Inet6Address($addr, true), $subnetSize);
   }
 
   /** @return string */
-  public function toString() {
-    return nameof($this).'('.$this->asString().')';
-  }
+  public function toString() { return nameof($this).'('.$this->asString().')'; }
 
   /** @return string */
-  public function hashCode() {
-    return $this->asString();
-  }
+  public function hashCode() { return $this->asString(); }
 
   /**
    * Compare