find key in array php

// Here's our fruity array
$fruits = ['apple', 'pear', 'banana'];

// Use it in an `if` statement
if (array_key_exists("banana", $fruits)) {
 // Do stuff because `banana` exists
}

// Store it for later use
$exists = array_key_exists("peach", $fruits);<?php
$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');

$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array);   // $key = 1;
?>

$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'));$arr = array(
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "seventeen" => 17
);
function find($mot){
  
  global $arr; // this is global variable
  $ok=false;
 foreach ($arr as $k => $v) 
    {
      if($k==$mot){
        return $v; $ok=true; // or return true;
      }
    }
  if(ok==false){ return -1; }  // or return false;
}

//call function
echo find("two");<?php
$search_array = array('first' => null, 'second' => 4);

// returns false
isset($search_array['first']);

// returns true
array_key_exists('first', $search_array);
?>

function findKey($array, $keySearch)
{
    foreach ($array as $key => $item) {
        if ($key == $keySearch) {
            echo 'yes, it exists';
            return true;
        } elseif (is_array($item) && findKey($item, $keySearch)) {
            return true;
        }
    }
    return false;
}