PHP How to get key name from value if array is multidimensional - php

Question

I have following array and getting this result:
Array
(
[0] => stdClass Object
(
[UnitIdx] => 10
[Title] => 순차
[Description] =>
[NumSteps] => 9
[ThumbnailPathName] => Level_1_Unit_thumbnail_Small.png
[Step_1] => 4
[Step_2] => 5
[Step_3] => 6
[Step_4] => 7
[Step_5] => 8
[Step_6] => 9
[Step_7] => 10
[Step_8] => 11
[Step_9] => 12
[Step_10] => 0
[Step_11] => 0
[Step_12] => 0
[Step_13] => 0
[Step_14] => 0
[Step_15] => 0
[Step_16] => 0
[Step_17] => 0
[Step_18] => 0
[Step_19] => 0
[Step_20] => 0
)
)
Now I want to find key form value. For example value is 11 so key is Step_8.
Any idea how to return key name from value?
Thanks.

Answer 1

You can search your key by value using array_search() and converting your Object into PHP array by typecasting, below is an example:
<?php
$object = array();
$object[0] = new StdClass;
$object[0]->foo = 1;
$object[0]->bar = 2;
echo "<pre>";
print_r($object);
echo "</pre>";
$key = array_search ('2', (array) $object[0]);
echo "<pre>";
print_r($key);
?>
Output:
Array
(
[0] => stdClass Object
(
[foo] => 1
[bar] => 2
)
)
bar

Answer 2

Take a look at this:
<?php
//this part of code is for prepare sample data which is similar to your data
$class = new stdClass;
$class->prop1 = 'prop1';
$class->prop2 = 'prop2';
$array = array($class);
//THIS IS METHOD FOR SEARCH KEY BY VALUE
print_r(array_search('prop1',json_decode(json_encode($array[0]), true))); //you are looking for key for value 'prop1'
Check working fiddle: CLICK!
Explanation:
1) json_decode(json_encode($array[0]), true) - because you have in your array stdClass object, you can't use array_search function. So this line converts $array[0] element, which is stdClass object to an array. Now we can use array_search function to search key by specific value.
2) print_r(array_search('prop1',json_decode(json_encode($array[0]), true))); - we are using array_search function to get key of array element which value is equal to prop1. Documentation of this function says:
array_search — Searches the array for a given value and returns the
corresponding key if successful
So we getting key corresponding to prop1 value, which is prop1. print_r function shows us result. Instead of that you can assign result of operation to a variable and use it in other parts of code, for example:
$variable = array_search('prop1',json_decode(json_encode($array[0]), true));