php get key list from array code example

Example 1: get key of array element php

$people = array(
  2 => array(
    'name' => 'John',
    'fav_color' => 'green'
  ),
  5=> array(
    'name' => 'Samuel',
    'fav_color' => 'blue'
  ));
$found_key = array_search('blue', array_column($people, 'fav_color'));

Example 2: how to get array key in php

<?php
$array = array(
    'fruit1' => 'apple',
    'fruit2' => 'orange',
    'fruit3' => 'grape',
    'fruit4' => 'apple',
    'fruit5' => 'apple');

// this cycle echoes all associative array
// key where value equals "apple"
for($i = 0; $i< sizeof($array);$i++){
if (key($array[$i]) == 'apple') {
        echo key($array).'<br />';
    }
    //next($array);
}
?>