To quickly fill a PHP array, use the array_fill() function to initialize a fixed-length array and set a default value; for associative arrays, you can combine array_combine() and array_fill() or loop assignments. 1.array_fill(start_index, count, value) is used for index array filling; 2. Associated arrays can be assigned one by one by array_combine($keys, array_fill(...))) or traversal key names; 3. Note that count cannot be a negative number, the fill value can be of any type, but the reference type needs to be modified carefully.

Sometimes you need to quickly fill a PHP array with specific values, such as initializing a fixed-length array, setting each element to 0 or a default string. PHP provides several ways to achieve this requirement, which is both simple and efficient.

Initialize a fixed length array and fill in default values

If you know the length of the array and want to set all elements to the same value, you can use array_fill() function. Its usage is straightforward:

 array_fill(start_index, count, value)

• start_index is the starting index (usually starting from 0)
• count is the number of elements to be filled
• value is the value you want to fill

For example, create an array of length 5, each element is 'hello' :

 $values ??= array_fill(0, 5, 'hello');
// Results: ['hello', 'hello', 'hello', 'hello', 'hello']

This method is very suitable for initializing configuration items, placeholders, or template data.

Several ways to fill an associative array

If you want to fill in an associative array (that is, the type with key names), array_fill() is not suitable. At this time, you can combine array_combine() and array_fill() to implement it:

 $keys = ['a', 'b', 'c'];
$values ??= array_fill(0, count($keys), 0);
$result = array_combine($keys, $values);
// Result: ['a' => 0, 'b' => 0, 'c' => 0]

You can also use a loop to assign values ??one by one. Although the code is multiple, it is more intuitive:

 $keys = ['x', 'y', 'z'];
$result = [];

foreach ($keys as $key) {
    $result[$key] = null;
}

Notes and tips

In actual use, there are several points that are easily overlooked:

• If count you pass in is 0 or negative, array_fill() will throw a warning or return an empty array.
• Indexes do not necessarily start from 0, but be careful not to cause index confusion.
• The filled value can be of any type, including reference types such as arrays, objects, etc., but be careful of side effects in subsequent modifications.

If you just need a numeric index array with all default values, it is recommended to use array_fill() first, which is concise and efficient.

Basically these methods. The operation is not complicated, but pay attention to index and quantity control, and don't let the array exceed expectations.

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