What happens when using non-strings or integers as key names?

In PHP, the type of array key name is very important. Usually we use integers or strings as key names for arrays, but if we use other types of values ​​as key names, it may lead to some unexpected results. This article will discuss potential issues that can occur when using non-strings or integers as array key names in PHP and how to deal with them.

1. Key names of non-strings and integers will be converted

PHP has certain specifications for array key names. Any data type that is not a string or an integer will be automatically converted to a string when used as a key name. PHP will try to convert key names to string types. If it is a complex data type such as objects, arrays, etc., PHP will use its specific conversion rules.

For example, if we use a floating point number as the key name of an array, PHP will automatically convert it to a string:

 <?php
$array = array();
$array[1.5] = "value";
echo $array["1.5"];  // Output "value"
?>

In the above code, although we used the floating number 1.5 as the key name, it is automatically converted to the string "1.5" and is successfully stored in the array. If you use the string "1.5" during access, the corresponding value can still be found correctly.

2. Use an object or array as key name

If we try to use an object or array as the key names of the array, PHP will report an error or convert them to a string. Specific behaviors vary according to the implementation of objects or arrays.

Object as array key name

When we use an object as the key name of an array, PHP will call the object's __toString() method (if the method exists) and use the return value of the method as the key name of the array. If the __toString() method is not defined, PHP will throw an error.

 <?php
class MyClass {
    public function __toString() {
        return "my_object";
    }
}

$obj = new MyClass();
$array = array();
$array[$obj] = "value";
echo $array["my_object"];  // Output "value"
?>

If the __toString() method is not defined, PHP will throw the following error:

 Catchable fatal error: Object of class MyClass could not be converted to string

Array as array key name

If we directly use an array as the key name of the array, PHP will try to convert it to a string, and the result will be an empty string ( "" ). This conversion usually results in key-value conflicts in arrays, especially when we have multiple arrays as keys, all of the keys become the same empty string.

 <?php
$array = array();
$array[array(1, 2)] = "value";
var_dump($array);  // mistake，The key name is converted to an empty string
?>

Output result:

 array(1) {
  [""]=> string(5) "value"
}

3. Summary

In PHP, array key names must be integers or strings, and other data types will be automatically converted to strings, but this may lead to some unexpected results, such as array key conflicts or unpredictable behavior.

• Integers and Strings : PHP correctly handles integers and strings as array key names.

• Floating point number : Floating numbers are automatically converted to strings (for example "1.5" ).

• Object : Objects will be converted into strings, which are determined by the __toString() method.

• Array : The array will be converted to an empty string.

During development, it is best to avoid using non-strings or non-integrals as array key names to avoid unpredictable problems. If you do need to use other types as key names, you can consider doing type conversion before use or implementing appropriate conversion logic.