## Setting and Getting Property Values

The following examples assume $company is the root of a tree of data objects created from the schema and instance document shown above.

Example #1 Access via property name

Data object properties can be accessed using the object property access syntax. The following sets the company name to 'Acme'.

`<?php
$company->name = 'Acme';
?>`

Example #2 Access via property name as array index

We can also access properties using associative array syntax. The simplest form of this uses the property name as the array index. For example, the following sets the company name and gets the employeeOfTheMonth.

`<?php
$company['name'] = 'UltraCorp';
$eotm = $company['employeeOfTheMonth'];
?>`

Example #3 Data Object iteration

We can iterate over the properties of a data object using foreach. The following iterates over the properties of the employee of the month.

`<?php
$eotm = $company->employeeOfTheMonth;
foreach ($eotm as $name => $value) {
echo "$name: $value\n";
}
?>`

which will output:

    name: Jane Doe
    SN: E0003

The 'manager' property is not output, because it has not been set.

Example #4 Access many-valued property by name

Many-valued data object properties can also be accessed using the object property name syntax. The following gets the list of departments.

`<?php
$departments = $company->departments;
?>`

Example #5 Many-valued element access

We can access individual elements of many-valued properties using array syntax. The following accesses the first department in the company.

`<?php
$ad_tech_dept = $company->departments[0];
?>`

Example #6 Many-valued property iteration

Many-valued properties can also be iterated over using foreach. The following iterates over the company's departments.

`<?php
foreach ($company->departments as $department) {
// ...
}
?>`

Each iteration will assign the next department in the list to the variable $department.

Example #7 Chained property access

We can chain property references on a single line. The following sets and gets the name of the first department.

`<?php
$company->departments[0]->name = 'Emerging Technologies';
$dept_name = $company->departments[0]->name;
?>`

Using the associative array syntax, this is equivalent to

`<?php
$company['departments'][0]['name'] = 'Emerging Technologies';
$dept_name = $company['departments'][0]['name'];
?>`

In either case, the dept_name variable is set to 'Emerging Technologies'.

Example #8 XPath navigation

The associative array index can be an XPath-like expression. Valid expressions are defined by an augmented sub-set of XPath.

Two forms of indexing into many-valued properties are supported. The first is the standard XPath array syntax with the indexing starting at one, the second is an SDO extension to XPath with an index starting at zero. The standard syntax is:

`<?php
$jane_doe = $company["departments[1]/employees[2]"];
?>`

and the SDO XPath extension syntax is:

`<?php
$jane_doe = $company["departments.0/employees.1"];
?>`

Both these examples get the second employee from the first department.

Example #9 XPath querying

We can use XPath to query and identify parts of a data object based on instance data. The following retrieves the manager from the 'Advanced Technologies' department.

`<?php
$ad_tech_mgr =
$company["departments[name='Advanced Technologies']/employees[manager=true]"];
?>`

Example #10 Creating child data objects

A data object can be a factory for its child data objects. A child data object is automatically part of the data graph. The following add a new employee to the 'Advanced Technologies' department.

`<?php
$ad_tech_dept = $company["departments[name='Advanced Technologies']"];
$new_hire = $ad_tech_dept->createDataObject('employees');
$new_hire->name = 'John Johnson';
$new_hire->SN = 'E0005';
$new_hire->manager = false;
?>`

Example #11 Unset a primitive property

We can use the isset() and unset() functions to test and remove items from the data object.

The following clears the name of the first department.

`<?php
unset($company->departments[0]->name);
?>`

Example #12 Unset a data object

unset can also be used to remove a data object from the tree. The following example shows John Jones leaving the company.

`<?php
unset($company->departments[0]->employees[0]);
?>`

Example #13 Unset a referenced data object

The following removes the 'employeeOfTheMonth' from the company. If this were a containment relationship then the employee would be removed from the company (probably not a good idea to sack your best employee each month!), but since this is a non-containment reference, the employee being referenced will remain in the department in the company, but will no longer be accessible via the employeeOfTheMonth property.

`<?php
if (isset($company->employeeOfTheMonth)) {
unset($company->employeeOfTheMonth);
}
?>`

Example #14 Access via property index

Data object properties can be accessed via their property index using array syntax. The property index is the position at which the property's definition appears in the model (in this case the xml schema). We can see from the schema listing above that the company name attribute is the second company property (the SDO interface makes no distinction between XML attributes and elements). The following sets the company name to 'Acme', with the same result as Access via property name

`<?php
$company[1] = 'Acme';
?>`

Using the index directly in this way is likely to be fragile. Normally the property name syntax should be preferred, but the property index may be required in special cases.