How to Create a SOAP API with PHP: A Detailed Tutorial and Code Examples

Introduction to SOAP API

SOAP (Simple Object Access Protocol) is a protocol based on XML that is used for exchanging structured information and is widely used to create Web services. SOAP APIs allow interaction between different operating systems and programming languages and support various protocols and standards.

In this article, we will demonstrate how to create a SOAP API using PHP, helping you understand the basic operations of the SOAP protocol.

Prerequisites

Before you start writing SOAP APIs, the following basic knowledge will be helpful:

• Basic understanding of the SOAP protocol
• Fundamental PHP programming skills

Creating a SOAP Server

To create a SOAP API in PHP, you need to set up a SOAP server on the server-side. Below is a simple example:

// Create SOAP server
$server = new SoapServer("example.wsdl");
// Register API function
function sayHello($name) {
  return "Hello, " . $name;
}
$server->addFunction("sayHello");
// Handle request
$server->handle();

Explanation of Code

In the above code, we first create a SOAP server and specify the path to the WSDL file. The WSDL file describes the functions and parameters of your SOAP service.

Next, we define a simple API function `sayHello`, which takes a `$name` parameter and returns a string. Finally, we add the function to the SOAP server using `addFunction` and call `handle()` to process the requests.

Creating a SOAP Client

To interact with the SOAP API, you need to create a SOAP client. Below is a code example for the client:

// Create SOAP client
$client = new SoapClient("example.wsdl");
// Call API function
$response = $client->sayHello("World");
echo $response;  // Output "Hello, World"

Explanation of Code

In the client code, we create a SOAP client and specify the path to the WSDL file. Then we call the `sayHello` function and pass "World" as a parameter.

Finally, we output the returned string `"Hello, World"`.

Passing Complex Data Types with SOAP API

In addition to simple data types, SOAP API can also pass complex objects and arrays. Below is an example of using an object as a parameter:

// Create object
class Person {
  public $name;
  public $age;
}
// Create SOAP server
$server = new SoapServer("example.wsdl");
// Register API function
function sayHelloToPerson($person) {
  return "Hello, " . $person->name . " (" . $person->age . ")";
}
$server->addFunction("sayHelloToPerson");
// Handle request
$server->handle();

In the above code, we define a `Person` class with two properties: `name` and `age`. Then, we define the function `sayHelloToPerson`, which accepts a `Person` object and returns a string containing the object's properties.

The client can pass a `Person` object like this:

// Create object
$person = new stdClass();
$person->name = "John";
$person->age = 30;
// Create SOAP client
$client = new SoapClient("example.wsdl");
// Call API function
$response = $client->sayHelloToPerson($person);
echo $response;  // Output "Hello, John (30)"

Explanation of Code

In the client code, we first create a `Person` object and set the `name` and `age` properties. Then, we create a SOAP client and call the `sayHelloToPerson` function, passing the object. Finally, we output the result.

Conclusion

Now that you have learned how to create a SOAP API using PHP, you can use the SOAP protocol to create various types of web services and interact with different systems. SOAP provides a powerful and reliable solution for developing cross-platform web services, especially in scenarios requiring high security.