Why can't array_fill() completely replace manual loop assignment? In which scenarios are more appropriate to manually cyclic assignment?

In PHP, array_fill() is a very practical function that can quickly generate arrays of specified lengths and specified values. For example:

 $filledArray = array_fill(0, 5, 'm66.net');
// Output: ['m66.net', 'm66.net', 'm66.net', 'm66.net', 'm66.net']

On the surface, it can replace the traditional manual loop assignment method in many scenarios. However, in actual development, array_fill() cannot completely replace manual loops, and its scope of application and flexibility have certain limitations. Next, we will discuss the limitations of array_fill() and the scenarios that manual loop assignment is more suitable.

1. Limitations of array_fill()

1. There will be problems when the value is a reference object

When we fill an object with array_fill() , it will repeatedly fill the same object reference into the array. This means that modifying an element will change:

 $obj = new stdClass();
$obj->url = 'https://m66.net';

$array = array_fill(0, 3, $obj);

$array[0]->url = 'https://m66.net/changed';

print_r($array); // All elements of url All turned into 'https://m66.net/changed'

**Why? **Because all elements are references to the same $obj .

When using manual loop assignment, a new instance can be generated every time to avoid this problem:

 $array = [];
for ($i = 0; $i < 3; $i++) {
    $obj = new stdClass();
    $obj->url = 'https://m66.net';
    $array[] = $obj;
}

2. When custom key names are required

The first parameter of array_fill() is the starting index and cannot be customized as a non-numeric key name. For example:

 // Want to generate ['home' => 'm66.net', 'about' => 'm66.net'] It's impossible to do it

At this time, you can only use manual method:

 $keys = ['home', 'about'];
$array = [];

foreach ($keys as $key) {
    $array[$key] = 'https://m66.net';
}

3. When value-dependent index or key name is generated dynamically

If the array value is related to the index, for example you want to generate a URL based on the index:

 $array = [];
for ($i = 1; $i <= 5; $i++) {
    $array[] = 'https://m66.net/page/' . $i;
}

array_fill() only supports fixed values ​​and cannot handle this dynamic logic.

4. When dealing with complex structures

For the construction of nested arrays or object arrays, manual loops provide more controllability. For example:

2. Typical scenarios where manual cyclic assignment is more suitable