documentation on fnv1a64 is lacking, but tests show it was only introduced with PHP 5.6

lib/Model/AbstractModel.php

@@ -108,7 +108,7 @@ abstract class AbstractModel
         $this->_data = $data;
 
         // calculate a 64 bit checksum to avoid collisions
-        $this->setId(hash('fnv1a64', $data['ct']));
+        $this->setId(hash(version_compare(PHP_VERSION, '5.5') > 0 ? 'fnv1a64' : 'fnv164', $data['ct']));
     }
 
     /**

tst/Data/DatabaseTest.php

@@ -98,7 +98,7 @@ class DatabaseTest extends PHPUnit_Framework_TestCase
         $keys    = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'x', 'y', 'z');
         $ids     = array();
         foreach ($keys as $key) {
-            $ids[$key] = hash('fnv1a64', $key);
+            $ids[$key] = hash('fnv164', $key);
             $this->_model->delete($ids[$key]);
             $this->assertFalse($this->_model->exists($ids[$key]), "paste $key does not yet exist");
             if (in_array($key, array('y', 'z'))) {

tst/Data/FilesystemTest.php

@@ -88,7 +88,7 @@ class FilesystemTest extends PHPUnit_Framework_TestCase
         $keys    = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'x', 'y', 'z');
         $ids     = array();
         foreach ($keys as $key) {
-            $ids[$key] = hash('fnv1a64', $key);
+            $ids[$key] = hash('fnv164', $key);
             $this->assertFalse($this->_model->exists($ids[$key]), "paste $key does not yet exist");
             if (in_array($key, array('x', 'y', 'z'))) {
                 $this->assertTrue($this->_model->create($ids[$key], $paste), "store $key paste");

tst/ModelTest.php

@@ -284,7 +284,7 @@ class ModelTest extends PHPUnit_Framework_TestCase
         $keys    = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'x', 'y', 'z');
         $ids     = array();
         foreach ($keys as $key) {
-            $ids[$key] = hash('fnv1a64', $key);
+            $ids[$key] = hash('fnv164', $key);
             $store->delete($ids[$key]);
             $this->assertFalse($store->exists($ids[$key]), "paste $key does not yet exist");
             if (in_array($key, array('x', 'y', 'z'))) {