Creating a simple SOAP client

Using SOAP, in contrast to the process of implementing a REST client or server, is quite easy as there is a PHP SOAP extension that provides both capabilities.

Note

A frequently asked question is "what is the difference between SOAP and REST?" SOAP uses XML internally as its data format. SOAP uses HTTP but only for transport, and otherwise has no awareness of other HTTP methods. REST directly operates HTTP, and can use anything for data formats, but JSON is preferred. Another key difference is that SOAP can operate in conjunction with a WSDL, which makes the service self-describing, thus more publicly available. Thus, SOAP services are often offered by public institutions such as national health organizations.

How to do it...

For this example, we will make a SOAP request for an existing SOAP service offered by the United States National Weather service:

The first consideration is to identify the WSDL document. The WSDL is an XML document that describes the service:
```
$wsdl = 'http://graphical.weather.gov/xml/SOAP_server/'
  . 'ndfdXMLserver.php?wsdl';
```

Next, we create a soap client instance using the WSDL:

$soap = new SoapClient($wsdl, array('trace' => TRUE));

We are then free to initialize some variables in anticipation of a weather forecast request:

$units = 'm';
$params = '';
$numDays = 7;
$weather = '';
$format = '24 hourly';
$startTime = new DateTime();

We can then make a LatLonListCityNames() SOAP request, identified as an operation in the WSDL, for a list of cities supported by the service. The request is returned in XML format, which suggests creating a SimpleXLMElement instance:
```
$xml = new SimpleXMLElement($soap->LatLonListCityNames(1));
```
Unfortunately, the list of cities and their corresponding latitude and longitude are in separate XML nodes. Accordingly, we use the array_combine() PHP function to create an associative array where latitude/longitude is the key, and the city name is the value. We can then later use this to present an HTML SELECT drop-down list, using asort() to alphabetize the list:
```
$cityNames = explode('|', $xml->cityNameList);
$latLonCity = explode(' ', $xml->latLonList);
$cityLatLon = array_combine($latLonCity, $cityNames);
asort($cityLatLon);
```

We can then get city data from a web request as follows:

$currentLatLon = (isset($_GET['city'])) ? strip_tags(urldecode($_GET['city'])) : '';

The SOAP call we wish to make is NDFDgenByDay(). We can determine the nature of the parameters supplied to the SOAP server by examining the WSDL:

<message name="NDFDgenByDayRequest">
<part name="latitude" type="xsd:decimal"/>
<part name="longitude" type="xsd:decimal"/>
<part name="startDate" type="xsd:date"/>
<part name="numDays" type="xsd:integer"/>
<part name="Unit" type="xsd:string"/>
<part name="format" type="xsd:string"/>
</message>

If the value of $currentLatLon is set, we can process the request. We wrap the request in a try {} catch {} block in case any exceptions are thrown:

if ($currentLatLon) {
  list($lat, $lon) = explode(',', $currentLatLon);
  try {
      $weather = $soap->NDFDgenByDay($lat,$lon,
        $startTime->format('Y-m-d'),$numDays,$unit,$format);
  } catch (Exception $e) {
      $weather .= PHP_EOL;
      $weather .= 'Latitude: ' . $lat . ' | Longitude: ' . $lon;
      $weather .= 'ERROR' . PHP_EOL;
      $weather .= $e->getMessage() . PHP_EOL;
      $weather .= $soap->__getLastResponse() . PHP_EOL;
  }
}
?>

How it works...

Copy all the preceding code into a chap_07_simple_soap_client_weather_service.php file. You can then add view logic that displays a form with the list of cities, as well as the results:

<form method="get" name="forecast">
<br> City List: 
<select name="city">
<?php foreach ($cityLatLon as $latLon => $city) : ?>
<?php $select = ($currentLatLon == $latLon) ? ' selected' : ''; ?>
<option value="<?= urlencode($latLon) ?>" <?= $select ?>>
<?= $city ?></option>
<?php endforeach; ?>
</select>
<br><input type="submit" value="OK"></td>
</form>
<pre>
<?php var_dump($weather); ?>
</pre>

Here is the result, in a browser, of requesting the weather forecast for Cleveland, Ohio:

Table of Contents for
PHP 7: Real World Application Development

Creating a simple SOAP client

Note

How to do it...

How it works...

See also

Table of Contents for PHP 7: Real World Application Development

Creating a simple SOAP client

Note

How to do it...

How it works...

See also

Table of Contents for
PHP 7: Real World Application Development