key
    (PHP 3, PHP 4 )
key -- Fetch a key from an associative array
Description
mixed 
key ( array array)
     key() returns the index element of the
     current array position.
    
     
Example 1. key() example <?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);
}
?> |  
  | 
    
     See also current() and next().