Fix PHP 8.1 compatibility.

When using this library with PHP 8.1, a deprecation warning is triggered: fwrite(): Passing null to parameter #2 ($data) of type string is deprecated
(see: phayes#190)

geoPHP.inc

@@ -223,7 +223,7 @@ class geoPHP
   // It could make a mistake in XML detection if you are mixing or using namespaces in weird ways (ie, KML inside an RSS feed)
   static function detectFormat(&$input) {
     $mem = fopen('php://memory', 'r+');
-    fwrite($mem, $input, 11); // Write 11 bytes - we can detect the vast majority of formats in the first 11 bytes
+    fwrite($mem, (string) $input, 11); // Write 11 bytes - we can detect the vast majority of formats in the first 11 bytes
     fseek($mem, 0);
 
     $bytes = unpack("c*", fread($mem, 11));

lib/adapters/EWKB.class.php

@@ -19,7 +19,7 @@ public function read($wkb, $is_hex_string = FALSE) {
 
     // Open the wkb up in memory so we can examine the SRID
     $mem = fopen('php://memory', 'r+');
-    fwrite($mem, $wkb);
+    fwrite($mem, (string) $wkb);
     fseek($mem, 0);
     $base_info = unpack("corder/ctype/cz/cm/cs", fread($mem, 5));
     if ($base_info['s']) {

lib/adapters/WKB.class.php

@@ -38,7 +38,7 @@ public function read($wkb, $is_hex_string = FALSE) {
     }
 
     $mem = fopen('php://memory', 'r+');
-    fwrite($mem, $wkb);
+    fwrite($mem, (string) $wkb);
     fseek($mem, 0);
 
     $geometry = $this->getGeometry($mem);