Access array where key is a variable - php

Question

$furtherKeys = "['book']['title']";
echo $this->json['parent'] . $furtherKeys;
This breaks. Is there anyway to do something like this?
I know you could explode $furtherKeys, count it, and setup a loop to achieve this, but I'm just curious if there is a direct way to concatenate an array with key names stored in a variable and have it work.
I want to use it for populating input field values from a json file. If I set a data-variable for each input field like:
<input type="text" data-keys="['book']['title']">
I could get the value of the data-variable, then just slap it onto the json object, and populate the value.
Thanks!

Answer 1

You can simply parse your build up array access using eval(). See my exaple here:
$example = array(
'foo' => array(
'hello' => array(
'world' => '!',
'earth' => '?'
)
),
'bar' => array());
// your code goes here
$yourVar = null;
$access = "['foo']['hello']['world']";
$actualAccesEvalCode = '$yourVar = $example'.$access.';';
eval($actualAccesEvalCode);
echo 'YourVal now is '.$yourVar;
Yet, i think it is better to use iteration. If $this->json['parent'] actually is an array, you write a recursive function to give you the result of the key.
See this ideone work here:
<?php
$example = array(
'foo' => array(
'hello' => array(
'world' => '!',
'earth' => '?'
)
),
'bar' => array());
function getArrayValueByKeyString($array,$keystring) {
$dotPosition = stripos ($keystring , '.' );
if($dotPosition !== FALSE) {
$currentKeyPart = substr($keystring, 0, $dotPosition);
$remainingKeyPart = substr($keystring, $dotPosition+1);
if(array_key_exists($currentKeyPart, $array)) {
return getArrayValueByKeyString(
$array[$currentKeyPart],
$remainingKeyPart);
}
else {
// Handle Error
}
}
elseif (array_key_exists($keystring, $array)) {
return $array[$keystring];
}
else {
// handle error
}
}
echo '<hr/>Value found: ' . getArrayValueByKeyString($example,'foo.hello.world');

Answer 2

Although I don't know how to do this with both book and title at the same time, it is possible to use variables as key names using curly braces.
// SET UP AN ARRAY
$json = array('parent' => array('book' => array('title' => 'The Most Dangerous Game')));
// DEFINE FURTHER KEYS
$furtherKeys1 = "book";
$furtherKeys2 = "title";
// USE CURLY BRACES TO INSERT VARIABLES AS KEY NAMES INTO YOUR PRINT STATEMENT
print "The Parent Book Title Is: ".$json['parent']{$furtherKeys1}{$furtherKeys2};
This outputs:
The Parent Book Title Is: The Most Dangerous Game