PHP Array Exercises : Identify the email addresses which are not unique

PHP Array: Exercise-41 with Solution

Write a PHP program to identify the email addresses which are not unique.

Sample Solution:

PHP Code:

function array_not_unique($my_array) {
    $same = array();
    reset ($my_array);

    $old_key    = NULL;
    $old_value    = NULL;
    foreach ($my_array as $key => $value) {
        if ($value === NULL) { continue; }
        if ($old_value == $value) {
            $same[$old_key]    = $old_value;
            $same[$key]        = $value;
        $old_value    = $value;
        $old_key    = $key;
return $same;

$test_array = array();
$test_array[1]    = '[email protected]';
$test_array[2]    = '[email protected]';
$test_array[3]    = '[email protected]';
$test_array[4]    = '[email protected]';


Sample Output:

    [1] => [email protected]                                          
    [3] => [email protected]                                          


Flowchart: PHP - Identify the email addresses which are not unique

PHP Code Editor:

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Next: Write a PHP function to find unique values from multidimensional arrays and flatten them in 0 depth.

What is the difficulty level of this exercise?

PHP: Tips of the Day

Convert a PHP object to an associative array

Just typecast it

$array = (array) $yourObject;

From Arrays:

If an object is converted to an array, the result is an array whose elements are the object's properties. The keys are the member variable names, with a few notable exceptions: integer properties are unaccessible; private variables have the class name prepended to the variable name; protected variables have a '*' prepended to the variable name.These prepended values have null bytes on either side.

Example: Simple Object

$object = new StdClass;
$object->foo = 1;
$object->bar = 2;

var_dump( (array) $object );


array(2) {
  'foo' => int(1)
  'bar' => int(2)

Example: Complex Object

class Foo
    private $foo;
    protected $bar;
    public $baz;

    public function __construct()
        $this->foo = 1;
        $this->bar = 2;
        $this->baz = new StdClass;

var_dump( (array) new Foo );

Output (with \0s edited in for clarity):

array(3) {
  '\0Foo\0foo' => int(1)
  '\0*\0bar' => int(2)
  'baz' => class stdClass#2 (0) {}

Output with var_export instead of var_dump:

array (
  '' . "\0" . 'Foo' . "\0" . 'foo' => 1,
  '' . "\0" . '*' . "\0" . 'bar' => 2,
  'baz' =>

Typecasting this way will not do deep casting of the object graph and you need to apply the null bytes (as explained in the manual quote) to access any non-public attributes. So this works best when casting StdClass objects or objects with only public properties. For quick and dirty (what you asked for) it's fine.

Also see this in-depth blog post:

  • Fast PHP Object to Array conversion

Ref : https://bit.ly/3fqiV2E