假設目前有陣列

$fruits = [
    ['id'=>0,'fruit'=>'apple','sweetness'=>2,'price'=>20],
    ['id'=>1,'fruit'=>'banana','sweetness'=>4,'price'=>15],
    ['id'=>2,'fruit'=>'grape','sweetness'=>5,'price'=>80],
    ['id'=>3,'fruit'=>'orange','sweetness'=>1,'price'=>70],
];

array_map

用來更新陣列中的值，產生出新的陣列。

$nfruits = array_map(function($fruit){
    $fruit['price'] = $fruit['price'] *2;
    return $fruit;
},$fruits);
print_r($nfruits);

就能取得一個price翻倍的新陣列

另外，也能將function函式提到array_map外，也能得到相同的結果

function doublePrice($fruit)
{
    $fruit['price'] = $fruit['price'] *2;
    return $fruit;
}
$nfruits = array_map("doublePrice",$fruits);
print_r($nfruits);

也能利用array_map做到陣列之間的比較
array_map("function",陣列一,陣列二,...);

function doublePrice($fruit,$a)
{
    if($fruit['fruit'] == $a)
        return "same";
    return "different";
}
$array = array("apple","lemon","pineaple","orange");
$nfruits = array_map("doublePrice",$fruits,$array);
print_r($nfruits);