How to Access Object Properties with Numeric or Invalid Names in PHP?

Accessing Object Properties with Numeric or Invalid Names in PHP

When working with JSON data in PHP, it's possible to encounter objects with properties named as integers or non-valid variable names. This can lead to difficulties accessing these properties using standard dot notation.

Syntax Error with Numeric Keys

Consider the following example, where a JSON object is decoded using json_decode():

$myVar = json_decode($data);

This may produce an object like:

[highlighting] => stdClass Object
    (
        [448364] => stdClass Object
            (
                [Data] => Array
                    (
                        [0] => Tax amount liability is .......
                    )
            )
    )

Attempting to access the string value in key [0] using dot notation, as shown below, will result in a syntax error:

print $myVar->highlighting->448364->Data->0;

What's the Issue?

PHP cannot directly access object properties with numeric names because they are considered invalid variable names. This issue arises due to the way PHP parses property accessors.

Possible Solutions

Option 1: Manual Casting

To access the property, you can manually convert the object to an array using (array)$object. This allows you to access the numeric property as an array key:

$highlighting = (array)$myVar->highlighting;
$data = (array)$highlighting['448364']->Data;
$value = $data['0'];

Option 2: Curly Brace Syntax

An alternative method is to use curly brace syntax to access the property. However, this only works if the property name is not entirely numeric:

echo $myVar->highlighting->{'448364'}->Data->0; // OK!
echo $myVar->highlighting->{'123'}->Data->0; // Error!

Option 3: Recursive Casting Function

A more robust approach is to create a custom function that recursively converts objects to arrays:

function recursive_cast_to_array($o) {
    $a = (array)$o;
    foreach ($a as &$value) {
        if (is_object($value)) {
            $value = recursive_cast_to_array($value);
        }
    }

    return $a;
}

$arr = recursive_cast_to_array($myVar);
$value = $arr['highlighting']['448364']['Data']['0'];

Option 4: Using JSON Functions

Another option is to use the built-in JSON functions to recursively convert the object to an array:

$arr = json_decode(json_encode($myVar), true);
$value = $arr['highlighting']['448364']['Data']['0'];

This approach is convenient but requires the data to be UTF-8 encoded.

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