Php algorithm - How to achieve that without eval - php

Question

I have a class that keeps data stores/access data by using words.separated.by.dots keys and it behaves like the following:
$object = new MyArray()
$object->setParam('user.name','marcelo');
$object->setParam('user.email','some#email.com');
$object->getParams();
/*
array(
'user' => array(
'name' => 'marcelo',
'email' => 'some#email.com'
)
);
*/
It is working, but the method unsetParam() was horribly implemented. That happened because i didn't know how to achieve that without eval() function. Although it is working, I found that it was a really challenging algorithm and that you might find fun trying to achieve that without eval().
class MyArray {
/**
* #param string $key
* #return Mura_Session_Abstract
*/
public function unsetParam($key)
{
$params = $this->getParams();
$tmp = $params;
$keys = explode('.', $key);
foreach ($keys as $key) {
if (!isset($tmp[$key])) {
return $this;
}
$tmp = $tmp[$key];
}
// bad code!
$eval = "unset(\$params['" . implode("']['", $keys) . "']);";
eval($eval);
$this->setParams($params);
return $this;
}
}
The test method:
public function testCanUnsetNestedParam()
{
$params = array(
'1' => array(
'1' => array(
'1' => array(
'1' => 'one',
'2' => 'two',
'3' => 'three',
),
'2' => array(
'1' => 'one',
'2' => 'two',
'3' => 'three',
),
)
),
'2' => 'something'
);
$session = $this->newSession();
$session->setParams($params);
unset($params['1']['1']['1']);
$session->unsetParam('1.1.1');
$this->assertEquals($params, $session->getParams());
$this->assertEquals($params['1']['1']['2'], $session->getParam('1.1.2'));
}

Answer 1

Is this it?
<?php
$params = array(
'1' => array(
'1' => array(
'1' => array(
'1' => 'one',
'2' => 'two',
'3' => 'three',
),
'2' => array(
'1' => 'one',
'2' => 'two',
'3' => 'three',
),
)
),
'2' => 'something'
);
function unsetParam( &$array, $paramString ) {
$cur =& $array;
$splitted = explode( ".", $paramString );
$len = count( $splitted ) - 1;
for( $i = 0; $i < $len; ++$i ) {
if( isset( $cur[ $splitted[ $i ] ] ) ) {
$cur =& $cur[ $splitted[ $i ] ];
}
else {
return false;
}
}
unset( $cur[ $splitted[$i] ] );
}
unsetParam( $params, "1.1.1");
print_r( $params );
/*
Array
(
[1] => Array
(
[1] => Array
(
[2] => Array
(
[1] => one
[2] => two
[3] => three
)
)
)
[2] => something
)
*/

Answer 2

You could make your code easier if you only split to a multidimension array in your getParams method:
class MyArray {
private $params = array();
public function setParam($key, $value) {
$this->params[$key] = $value;
}
/**
* #param string $key
* #return Mura_Session_Abstract
*/
public function unsetParam($key)
{
unset($this->params[$key]);
return $this;
}
public function getParams() {
$retval = array();
foreach ($this->params as $key => $value) {
$aux = &$retval;
foreach (explode(".", $key) as $subkey) {
if (!isset($aux[$subkey])) $aux[$subkey] = array();
$aux = &$aux[$subkey];
}
$aux = $value;
}
return $retval;
}
}

Answer 3

#gustavotkg and #Esailija have both offered some great ideas. Here is another simple, easy to understand, and short approach that avoids unset() altogether (which can get quirky in some cases).
This would, of course, be most useful when $params is limited to less than, say, 1k-10k of values (which starts to get a bit pricey in the CPU/memory dept):
<?php
$params = array(
'1' => array(
'1' => array(
'1' => array(
'1' => 'one-one',
'2' => 'one-two',
'3' => 'one-three',
),
'2' => array(
'1' => 'two-one',
'2' => 'two-two',
'3' => 'two-three',
),
)
),
'2' => 'something'
);
function filterParams($params, $refKey, $base = '') {
$newvals = array();
foreach($params as $k=>$v) {
$joinedKey = $base? $base . '.' . $k : $k;
if( $joinedKey != $refKey ) {
$newvals[$k] = is_array($v)? filterParams($v, $refKey, $joinedKey) : $v;
}
}
return $newvals;
}
var_dump(filterParams($params, '1.1.2'));