Php 7.3 fix (#5434)

* Inherit from message instead of implement

When regestering class (implmenets other class) during MINIT, zend_class_implements
would call zend_class_entry->interface_gets_implemented(). In PHP-7.3 interface_gets_implemented shares the same location with create_object.
However, during MINIT, the global object storeage hasn't been initialized. And thus, caused segment fault in php 7.3.

* Use zend_string_init where interned string may be the value.
zend_string_dup will keep using the existing interned string.
In php 7.3, interned string cannot be destroyed from user's code.

* Uncommment debug code

* Use latest phpunit for each php versions

* Revert change in Dockerfile

* Update php test to use the new docker image

* Update composer

* Change docker organization

* Update phpunit

* Debug phpunit

* Store phpunit into bin dir in docker image

* Install valgrind to docker

* Fix compatibility test

* Remove generated_service_test from compatibility c extension test

* Update 32bit php test to the new docker image

* Install bison

* Fix build.sh

* Fix DOCKERIMAGE_PREFIX

* Fix basename

* Add comment to build_and_run_docker2.sh

* Remove commented code

* Fix comments
diff --git a/php/tests/generated_class_test.php b/php/tests/generated_class_test.php
index 96dad22..38c3809 100644
--- a/php/tests/generated_class_test.php
+++ b/php/tests/generated_class_test.php
@@ -260,12 +260,14 @@
     {
         $m = new TestMessage();
         $m->setOptionalNestedEnum(NestedEnum::ZERO);
+        $this->assertTrue(true);
     }
 
     public function testLegacyNestedEnum()
     {
         $m = new TestMessage();
         $m->setOptionalNestedEnum(\Foo\TestMessage_NestedEnum::ZERO);
+        $this->assertTrue(true);
     }
 
     public function testLegacyTypehintWithNestedEnums()
@@ -405,6 +407,7 @@
           $m = new TestMessage();
           $hex = hex2bin("ff");
           $m->setOptionalBytes($hex);
+          $this->assertTrue(true);
       }
 
     #########################################################
@@ -709,6 +712,8 @@
         // test nested messages
         $sub = new NoNamespaceMessage\NestedMessage();
         $n->setNestedMessage($sub);
+
+        $this->assertTrue(true);
     }
 
     public function testEnumWithoutNamespace()
@@ -718,6 +723,7 @@
         $repeatedNoNamespaceEnum = $m->getRepeatedNoNamespaceEnum();
         $repeatedNoNamespaceEnum[] = NoNameSpaceEnum::VALUE_A;
         $m->setRepeatedNoNamespaceEnum($repeatedNoNamespaceEnum);
+        $this->assertTrue(true);
     }
 
     #########################################################
@@ -1262,6 +1268,8 @@
         $m = \Upper_enum_value\NotAllowed::NULL;
         $m = \Upper_enum_value\NotAllowed::VOID;
         $m = \Upper_enum_value\NotAllowed::ITERABLE;
+
+        $this->assertTrue(true);
     }
 
     #########################################################
@@ -1297,6 +1305,7 @@
     {
         $m = new testLowerCaseMessage();
         $n = testLowerCaseEnum::VALUE;
+        $this->assertTrue(true);
     }
 
     #########################################################
@@ -1363,6 +1372,7 @@
         ]);
 
         TestUtil::assertTestMessage($m);
+        $this->assertTrue(true);
     }
 
     #########################################################