Wildcards in PHP functions - php

Question

I am not sure if the term "Wildcard" can explain my point, but sometimes in some ready scripts we are able to call a non defined function like find_by_age(23) where age can be anything else that's mapped to a database table record. So i can call find_by_name, find_by_email, find_by_id and so on. So how can we do such thing either in procedural or object oriented ways ?

Answer 1

The term you are looking for is magic method.
Basically like this:
class Foo {
public function __call($method,$args) {
echo "You were looking for the method $method.\n";
}
}
$foo = new Foo();
$foo->bar(); // prints "You were looking for the method bar."
For what you are looking for, you just filter out bad function calls and redirect good ones:
class Model {
public function find_by_field_name($field,$value) { ... }
public function __call($method,$args) {
if (substr($method,0,8) === 'find_by_') {
$fn = array($this,'find_by_field_name');
$arguments = array_merge(array(substr($method,8)),$args);
return call_user_func_array($fn,$arguments);
} else {
throw new Exception("Method not found");
}
}
}

Answer 2

You can use them by defining a __call magic method in your class, you can use them only in classes. on global scope
Quoting from PHP Manual:
<?php
class MethodTest {
public function __call($name, $arguments) {
// Note: value of $name is case sensitive.
echo "Calling object method '$name' "
. implode(', ', $arguments). "\n";
}
/** As of PHP 5.3.0 */
public static function __callStatic($name, $arguments) {
// Note: value of $name is case sensitive.
echo "Calling static method '$name' "
. implode(', ', $arguments). "\n";
}
}
$obj = new MethodTest;
$obj->runTest('in object context');
MethodTest::runTest('in static context'); // As of PHP 5.3.0
?>
The above example will output:
Calling object method 'runTest' in object context
Calling static method 'runTest' in static context

Answer 3

For a procedural solution you can simply use string concatenation to get the job done. You can also fancy things up a bit by calling it an implementation of the strategy pattern.
<?php
/**
* Employ a find by name strategy
*/
function find_by_name($name)
{
echo "You are searching for users with the name $name";
return array();
}
/**
* Employ a find by age strategy
*/
function find_by_age($age)
{
echo "You are searching for users who are $age years old";
return array();
}
/**
* Find users by using a particular strategy
*/
function find_using_strategy($strategy='age', $parameter)
{
$results = array();
$search_function = 'find_by_' . $search_field;
if (function_exists($search_function)) {
$results = $search_function($parameter);
}
return $results;
}
$users = find_using_strategy('name', 'Matthew Purdon');
var_dump($users);