What are the php array operations?

In PHP, array is a very commonly used data type. Arrays can store multiple values, and these values ​​can be retrieved and accessed through a unique key. In this article, we will introduce some basic PHP array operations along with sample code to help you understand them better.

1. Creating an array

There are two ways to create an array: one is to use the array() function, and the other is to use square brackets ([]). The following is sample code for both methods:

//使用array()函数创建数组
$array1 = array(1, 2, 3, 4, 5);

//使用方括号([])创建数组
$array2 = [1, 2, 3, 4, 5];

When creating an array, you can specify the key name and key value of the array, or you can omit the key name and let PHP automatically assign numeric keys.

//指定键名和键值
$array3 = array("name"=> "Tom", "age"=>20, "gender"=>"male");

//省略键名
$array4 = array(1, 2, 3, 4, 5);

2. Accessing array elements

There are two ways to access array elements: one is to use key names, and the other is to use indexes. Here is sample code for both ways:

//使用键名访问数组元素
echo $array3["name"];

//使用索引访问数组元素
echo $array4[2];

3. Modify array elements

You can modify elements in an array using key names or indexes.

//使用键名修改数组元素
$array3["age"] = 21;

//使用索引修改数组元素
$array4[2] = 9;

4. Traversing arrays

There are three ways to traverse arrays: for loop, foreach loop and while loop. The following is sample code for three methods:

//for循环遍历数组
for($i = 0; $i < count($array1); $i++)
{
    echo $array1[$i];
}

//foreach循环遍历数组
foreach($array3 as $key=>$value)
{
    echo $key.":".$value;
}

//while循环遍历数组
$i = 0;
while($i < count($array2))
{
    echo $array2[$i];
    $i++;
}

5. Array sorting

PHP provides a variety of array sorting functions.

//按照值升序排序
sort($array1);

//按照值降序排序
rsort($array1);

//按照键名升序排序
ksort($array3);

//按照键名降序排序
krsort($array3);

//根据自定义排序规则对数组排序（示例按照年龄升序排序）
function cmp($a, $b)
{
    if($a["age"] == $b["age"])
     return 0;
    return ($a["age"] < $b["age"]) ? -1 : 1;
}

usort($array5, "cmp");

6. Array Merge

You can use the array_merge function to merge two or more arrays into one array.

$array6 = array_merge($array1, $array2);

7. Array deduplication

Use the array_unique function to deduplicate duplicate elements in the array.

$array7 = [1, 2, 3, 3, 4, 4];
$array7 = array_unique($array7);

8. Array filtering

You can use the array_filter function to filter the elements of an array. The following example code will filter out elements less than 5 in the array.

function filter($value)
{
    return $value > 5;
}

$array8 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
$array8 = array_filter($array8, "filter");

9. Array slice

Use the array_slice function to slice the array and obtain elements within a certain range.

$array9 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
$array10 = array_slice($array9, 2, 5);

These are some basic PHP array operations. PHP arrays provide you with many convenient tools when you need to process data.

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