array_unshift 用于多维数组

array_unshift() 函数用于在数组的开头插入一个或多个元素。如果数组是一个关联数组，则插入的值会以数字键名的形式添加到数组的开头。

php
$fruits = array("apple", "banana", "orange");
array_unshift($fruits, "pear", "grape");
print_r($fruits);
?>

Array
(
    [0] => pear
    [1] => grape
    [2] => apple
    [3] => banana
    [4] => orange
)

php
$students = array(
    array("name" => "Alice", "age" => 20),
    array("name" => "Bob", "age" => 22),
    array("name" => "Charlie", "age" => 21)
);
$newStudent = array("name" => "David", "age" => 19);
array_unshift($students, $newStudent);
print_r($students);
?>

Array
(
    [0] => Array
        (
            [name] => David
            [age] => 19
        )
    [1] => Array
        (
            [name] => Alice
            [age] => 20
        )
    [2] => Array
        (
            [name] => Bob
            [age] => 22
        )
    [3] => Array
        (
            [name] => Charlie
            [age] => 21
        )
)