Function and usage of map_deep() in wordpress


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    The map_deep() function in WordPress is a versatile utility function used to apply a callback function to all non-iterable elements of a given array or object. This function is especially useful when you need to process or modify data within nested structures like arrays or objects.

    Function Definition:

    map_deep( mixed $value, callable $callback ): mixed

    Function Components:

    1. Parameters:

      • $value (mixed): This is the array, object, or scalar value to which the callback function will be applied. It's the input data that you're processing.
      • $callback (callable): This is the function that will be mapped onto $value. This function is applied to each non-iterable element found within $value.
    2. Return Value:

      • The function returns a modified version of $value, with the callback applied to all non-array and non-object elements inside it.

    How It Works:

    • map_deep() works similarly to array_walk_recursive(), but it has the added capability of handling objects in addition to arrays.
    • The function iterates through $value, and for each element that is not an array or an object (i.e., a scalar or a null value), it applies the $callback function.
    • The original structure of $value is maintained, but the non-iterable elements are altered according to the callback function.

    Example Usage:

    Suppose you have an array with nested arrays and you want to apply a function to all non-array elements. For example, let's say you want to sanitize all string values in a complex data structure.

    1. Define Your Callback Function:

      function sanitize_string($value) {
          // Example: sanitize the string for safe use in HTML
          return htmlspecialchars($value, ENT_QUOTES, 'UTF-8');
    2. Apply map_deep():

      $data = [
          'name' => 'John & Sons <script>',
          'age' => 30,
          'attributes' => [
              'hobbies' => ['<script>alert("hack")</script>', 'football']
      $sanitized_data = map_deep($data, 'sanitize_string');
    3. Result:

      • In this example, map_deep() will apply the sanitize_string function to all non-iterable elements of $data. The strings will be sanitized, but the array structure will remain the same.

    Use Cases:

    • Sanitizing input data.
    • Applying formatting functions to complex data structures.
    • General transformations of nested data where a simple array map is insufficient.


    • It's important to ensure that the callback function can handle the types of values it will encounter in $value.
    • The map_deep() function is part of the WordPress utility functions and is not available in standard PHP.

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