From 30eff69a10898dd9b2fb10ed07ae8c68458a5ad2 Mon Sep 17 00:00:00 2001
From: Emiel Bruijntjes
+ In PHP scripts you can define constants - both global constants and
+ class level constants. This can also be done with PHP-CPP. If you want
+ to expose constants to user space PHP code, you can do that by adding
+ the constants to the Php::Extension object inside the get_module()
+ call.
+
+Constants
+
+
+#include <phpcpp.h>
+
+/**
+ * Switch to C context so that the get_module() function can be
+ * called by C programs (which the Zend engine is)
+ */
+extern "C" {
+ /**
+ * Startup function for the extension
+ * @return void*
+ */
+ PHPCPP_EXPORT void *get_module() {
+ static Php::Extension myExtension("my_extension", "1.0");
+
+ // add integer constants
+ myExtension.add(Php::Constant("MY_CONSTANT_1", 1));
+ myExtension.add(Php::Constant("MY_CONSTANT_2", 2));
+
+ // floating point constants
+ myExtension.add(Php::Constant("MY_CONSTANT_3", 3.1415927));
+ myExtension.add(Php::Constant("MY_CONSTANT_4", 4.932843));
+
+ // string constants
+ myExtension.add(Php::Constant("MY_CONSTANT_5", "This is a constant value"));
+ myExtension.add(Php::Constant("MY_CONSTANT_6", "Another constant value"));
+
+ // null constants
+ myExtension.add(Php::Constant("MY_CONSTANT_7", nullptr));
+
+ // return the extension
+ return myExtension;
+ }
+}
+
+ It is all very straight forward. Using the constants in a PHP script is + just as easy: +
++
+<?php
+echo(MY_CONSTANT_1."\n");
+echo(MY_CONSTANT_2."\n");
+echo(MY_CONSTANT_3."\n");
+echo(MY_CONSTANT_4."\n");
+echo(MY_CONSTANT_5."\n");
+echo(MY_CONSTANT_6."\n");
+echo(MY_CONSTANT_7."\n");
+?>
+
+
++ PHP also supports the concept of class level constants. Internally, in + the Zend engine, class level constants are implemented as regular class + members, but instead of a "public" or "private" flag, a constant property + is marked with a "constant" flag. PHP-CPP exposes this too. You can + register class properties with a Php::Const flag. +
++ Besides this, a Php::Class instance also has a "constant" method, and + you can add instances of Php::Constant to the class. Semantically, all + these three ways to create class level constants are identical. +
++
+/**
+ * The C++ class that we're going to expose
+ *
+ * (For this example we use a completely empty class, as only examples
+ * are given on how to use constants)
+ */
+class Dummy : public Php::Base
+{
+};
+
+/**
+ * Switch to C context so that the get_module() function can be
+ * called by C programs (which the Zend engine is)
+ */
+extern "C" {
+ /**
+ * Startup function for the extension
+ * @return void*
+ */
+ PHPCPP_EXPORT void *get_module() {
+ static Php::Extension myExtension("my_extension", "1.0");
+
+ // create a class objects
+ Php::Class<Dummy> dummy("Dummy");
+
+ // there are many different ways to add constants, but semantically,
+ // they're all the same
+ dummy.property("MY_CONSTANT_1", 1, Php::Const);
+ dummy.property("MY_CONSTANT_2", "abcd", Php::Const);
+ dummy.constant("MY_CONSTANT_3", "xyz");
+ dummy.constant("MY_CONSTANT_4", 3.1415);
+ dummy.add(Php::Constant("MY_CONSTANT_5", "constant string"));
+ dummy.add(Php::Constant("MY_CONSTANT_5", true));
+
+ // add the class to the extension
+ myExtension.add(std::move(dummy));
+
+ // return the extension
+ return myExtension;
+ }
+}
+
+
++ If you want to find out the value of a user space constant at runtime + from your C++ code, or when you want to find out if a constant is + defined or not, you can simply use the Php::constant() or Php::defined() + functions. To define constants at runtime, use Php::define(): +
++
+/**
+ * Function that can be called from a PHP script
+ */
+void example_function()
+{
+ // check if a certain user space constant is defined
+ if (Php::defined("USER_SPACE_CONSTANT"))
+ {
+ // retrieve the value of a constant
+ Php::Value constant = Php::constant("ANOTHER_CONSTANT");
+
+ // define other constants at runtime
+ Php::define("DYNAMIC_CONSTANT", 12345);
+ }
+}
+
+/**
+ * Switch to C context so that the get_module() function can be
+ * called by C programs (which the Zend engine is)
+ */
+extern "C" {
+ /**
+ * Startup function for the extension
+ * @return void*
+ */
+ PHPCPP_EXPORT void *get_module() {
+ static Php::Extension myExtension("my_extension", "1.0");
+
+ // add a function to the extension
+ extension.add("example_function", example_function);
+
+ // return the extension
+ return myExtension;
+ }
+}
+
+
diff --git a/documentation/properties.html b/documentation/properties.html
index 6f3ece5..db7c44f 100644
--- a/documentation/properties.html
+++ b/documentation/properties.html
@@ -194,7 +194,13 @@ extern "C" {
The class constant can be accessed from PHP scripts using Example::MY_CONSTANT, - and the static properties with Example::$my_property. + and the static properties with Example::$my_property. +
++ Besides using the property() method, you can also + create class constants using the constant() method, or using the + Php::Constant class. More information about this can be found in our + article about constants.
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