Custom Implementation of array_flip Without Using PHP Array Functions

The array_flip function in PHP exchanges the keys and values of an array. Below is a custom implementation of this functionality without using PHP’s built-in array functions.

Code Example:

<?php
function custom_array_flip($array) {
    $result = [];

    // Loop through the array
    foreach ($array as $key => $value) {
        // Ensure the value can be used as a key
        if (is_scalar($value)) {
            $result[$value] = $key;
        }
    }

    return $result;
}

// Example usage
$inputArray = ['a' => 1, 'b' => 2, 'c' => 3];
$flippedArray = custom_array_flip($inputArray);
print_r($flippedArray);
?>

Output:

Array
(
    [1] => a
    [2] => b
    [3] => c
)

Explanation:

1. Input Parameter:
   • $array: The input array whose keys and values need to be swapped.
2. Result Initialization:
   • Create an empty $result array to store the flipped key-value pairs.
3. Iteration:
   • Use a foreach loop to iterate over the input array.
   • For each key-value pair:
     • Ensure the value is a scalar (string, integer, or float) because PHP keys must be scalar.
     • Add the value as the key and the key as the value in the $result array.
4. Output:
   • Return the $result array with flipped keys and values.

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