Php function default parameter constant

You can find this documentation page on GitHub. PHP has a mechanism to enforce the types of function parameters, and to accept parameters either by reference or by value. In the earlier examples , we had not yet used that mechanism, and we left it to the function implementations to inspect the 'Php:: Parameters' object which is a std:: Value objects , and to check whether the number of parameters is correct, and of the right type.

Above you see that we pass in additional information when we register the "example" function. We tell the PHP engine that our function accepts three parameters: Parameters instance, but the moment it gets called, you can be sure that the Php:: Parameters object will be filled with three members, and that two of them are objects of the appropriate type.

You may be surprised to see that we specified the first parameter to be of type Numeric. After all, in PHP there is no offical way to enforce the type of a scalar parameter.

PHP: Function arguments - Manual

When you write a function in PHP, it is possible to enforce that the function receives an object or an array, but not that you want to receive a string or an integer. The same is true for native functions.

Although the core PHP engine and PHP-CPP library both offer the possibility to specify that your function accepts parameters of type "Php:: Numeric" or of type "Php:: String", this setting is further completely ignored. Maybe this is going to change in the future let's hope so , but for now it is only meaningful to specify the parameter type for objects and arrays. We have however chosen to still offer this feature in PHP-CPP, because it is also offered by the core PHP engine, so that we are ready for future versions of PHP.

But for now the specification of the numeric parameter in our example is meaningless. The PHP engine will trigger an error if your function is called with wrong parameters, and will not make the actual call to the native function.

ByVal class that we showed can be constructed in two ways. The first parameter of the constructor should always be the parameter name.

PHP: Function arguments - Manual

This is a little strange, because PHP does not support the concept of 'named variables', like other languages do. Internally, this name is only used to generate an error messages when your function is called in the wrong way.

PHP function with variable as default value for a parameter - Stack Overflow

In practice, it only makes a difference if you specify Php:: Object as type, because all other types are not enforced by the underlying PHP engine. The final parameter do you remember that it was called 'required'? If you set it to true, PHP will trigger an error when your function is called without this parameter.

This setting only works for the trailing parameters, as it is of course not possible to mark the first parameter as optional, and all subsequent parameters as required. If you write a function that accepts an object as parameter, you can use the second form of the Php:: This alternative constructor also has a 'name' and 'required' parameter, but the Php:: Type parameter that was available before is now replaced by a 'classname' and 'nullable' parameter.

This constructor can be used for functions that accept an object of a specific type as parameter. For example, take a look at the following code in PHP:.

By the name of the Php:: ByVal class you may have concluded that there must also be a Php:: ByRef class - and you could not have been more right than that. There is indeed a Php:: If you create a function that takes a parameter by reference and that can thus 'return' a value via a parameter you can specify that too.

ByRef class has exactly the same signature as the Php:: ByVal class, and can be used in exactly the same way.

The difference is that ByRef also checks if someone tries to call your function with a literal instead of a variable - which is not possible for variables by reference. If this happens, an error is triggered and the function will not be called. Let's show an example. The following extension creates a function that swaps the contents of two variables.

When you add your native functions to the extension object, you may supply an optional third parameter with a list of Php:: ByRef objects with the names and types of the parameters that are accepted. Internally, the PHP engine runs a check right before every function call to verify that the passed in parameters are compatible with the parameter specification that you gave, and will trigger an error if they are not.

Specifying parameters is optional.

If you choose to leave this specification out it is up to you to check inside the function if there are enough parameters, and if the types are correct. PHP-CPP is made by Copernica , a leading provider of high quality marketing software located in Amsterdam, The Netherlands.

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Your first extension Generate output and errors Register native functions Function parameters Calling functions Lambda functions Classes and objects Constructors and destructors Class inheritance Magic methods Magic interfaces Special features Class properties Exceptions Working with variables Global and class level constants Loading settings from php. Specifying function parameters PHP has a mechanism to enforce the types of function parameters, and to accept parameters either by reference or by value.

ByVal "b", "ExampleClass" , Php:: Can you really enforce scalar parameters?

To come back to our example, the following functions calls can now be done from PHP user space: ByVal class further explained The Php:: Type parameter is more interesting. The following types are supported: Callable In practice, it only makes a difference if you specify Php:: For example, take a look at the following code in PHP: Who is behind PHP-CPP? We are hiring We're always looking for talented individuals to join our awesome team!

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