php get array key

                                    array_keys ($array);
// It returns an array
// more informations at https://www.php.net/manual/fr/function.array-keys.php (fr)

                                    <?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
foreach($age as $x=>$x_value)
  {
  echo "Key=" . $x . ", Value=" . $x_value;
  echo "<br>";
  }
?>

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

// this cycle echoes all associative array
// key where value equals "apple"
while ($fruit_name = current($array)) {
    if ($fruit_name == 'apple') {
        echo key($array).'<br />';
    }
    next($array);
}
?>

                                    
<?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;
?>

                                    $array = array(0 => 100, "cor" => "vermelho");
print_r(array_keys($array));

$array = array("azul", "vermelho", "verde", "azul", "azul");
print_r(array_keys($array, "azul"));

$array = array("cor"     => array("azul", "vermelho", "verde"),
               "tamanho" => array("pequeno", "medio", "grande"));
print_r(array_keys($array));