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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:

<?php
function array_not_unique($my_array) {
    $same = array();
    natcasesort($my_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]';

print_r(array_not_unique($test_array));
?>

Sample Output: 

Array                                                               
(                                                                   
    [1] => [email protected]                                          
    [3] => [email protected]                                          
)

Flowchart:

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

PHP Code Editor:

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Previous: Write a PHP program to get a sorted array without preserving the keys.
Next: Write a PHP function to find unique values from multidimensional arrays and flatten them in 0 depth.

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PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC