PHP Array Exercises : Find unique values from multidimensional array and flatten them in zero depth

Last update on May 30 2025 13:14:43 (UTC/GMT +8 hours)

42. Unique Flattened Values from Multidimensional Arrays

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

Sample Solution:

PHP Code:

<?php
// Define a function to flatten a multidimensional array
function array_flat($my_array) 
{ 
    // Initialize an array to store flattened values
    $fa = array();
    // Initialize a variable to track the recursion depth
    $l = 0;

    // Loop through the input array
    foreach($my_array as $k => $v ) 
    { 
        // Check if the current value is not an array
        if( !is_array( $v ) ) 
        { 
            // Add the non-array value to the flattened array
            $fa[] = $v; 
            // Continue to the next iteration
            continue;           
        } 

        // Increment the recursion depth
        $l++; 
        // Recursively flatten the nested array
        $fa = array_flat( $v, $fa, $l ); 
        // Decrement the recursion depth
        $l--; 
    } 

    // Check if the recursion depth is back to the top level
    if( $l == 0 ) 
        // Remove duplicates and re-index the array
        $fa = array_values( array_unique( $fa ) );         

    // Return the flattened array
    return $fa;       
} 

// Create a test multidimensional array
$tmp = array( 'a' => array( -1, -2, 0, 2, 3 ), 'b' => array( 'c' => array( -1, 0, 2, 0, 3 ) ) ); 

// Call the function and display the result
print_r(array_flat($tmp));
?>

Output:

Array                                                       
(                                                           
    [0] => -1                                               
    [1] => 0                                                
    [2] => 2                                                
    [3] => 3                                                
) 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a PHP function to recursively traverse a multidimensional array and return a flattened array of unique values.
• Write a PHP script to combine multiple nested arrays into one flat array while filtering duplicate entries.
• Write a PHP program to flatten a multidimensional array and remove duplicates using a custom iteration approach.
• Write a PHP function to merge nested arrays and then apply array_unique() to the flat result and output it.

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