Common methods of php arrays

In PHP development, array is a very commonly used data type. A PHP array is an ordered collection used to store a set of values. During the application development process, it is often necessary to operate on arrays, including operations such as adding, deleting, modifying, and querying. This article will introduce common methods of PHP arrays.

1. Creating Arrays

There are two ways to create PHP arrays: ordinary arrays and associative arrays.

Ordinary arrays access element values ​​by specifying the index number of the element, while associative arrays access element values ​​by specifying string key names.

Create a normal array:

// 方式1
$arr1 = array("a", "b", "c");
// 方式2
$arr2 = ["a", "b", "c"];

Create an associative array:

// 方式1
$arr1 = array("name" => "John", "age" => 30, "country" => "USA");
// 方式2
$arr2 = ["name" => "John", "age" => 30, "country" => "USA"];

2. Access array elements

You can use square brackets to access array elements [] operator. For a normal array, you can access elements using numeric indexes, and for associative arrays, you can access elements using key names.

// 访问普通数组
$arr = ["a", "b", "c"];
echo $arr[0]; // 输出a
echo $arr[1]; // 输出b
echo $arr[2]; // 输出c
 
// 访问关联数组
$user = ["name" => "John", "age" => 30, "country" => "USA"];
echo $user["name"]; // 输出John
echo $user["age"]; // 输出30
echo $user["country"]; // 输出USA

3. Array length

PHP provides the count() function to get the length of the array.

$arr = ["a", "b", "c"];
echo count($arr); // 输出3

4. Add elements

Elements can be added to the array through the square brackets [] operator.

// 添加元素到普通数组
$arr = ["a", "b", "c"];
$arr[] = "d"; // 在数组末尾添加元素d
print_r($arr); // 输出Array ( [0] => a [1] => b [2] => c [3] => d )
 
// 添加元素到关联数组
$user = ["name" => "John", "age" => 30];
$user["country"] = "USA"; // 添加元素到关联数组
print_r($user); // 输出Array ( [name] => John [age] => 30 [country] => USA )

5. Delete elements

You can delete elements in the array through the unset() function. For ordinary arrays, after deleting an element, the index numbers in the array will be reordered; for associative arrays, after deleting an element, the key names of all subsequent elements will be automatically adjusted.

// 删除普通数组中的元素
$arr = ["a", "b", "c"];
unset($arr[1]); // 删除索引号为1的元素b
print_r($arr); // 输出Array ( [0] => a [2] => c )
 
// 删除关联数组中的元素
$user = ["name" => "John", "age" => 30, "country" => "USA"];
unset($user["age"]); // 删除键名为age的元素
print_r($user); // 输出Array ( [name] => John [country] => USA )

6. Modify elements

You can modify elements in the array through the square brackets [] operator.

// 修改普通数组中的元素
$arr = ["a", "b", "c"];
$arr[1] = "d"; // 把索引号为1的元素b改为d
print_r($arr); // 输出Array ( [0] => a [1] => d [2] => c )
 
// 修改关联数组中的元素
$user = ["name" => "John", "age" => 30, "country" => "USA"];
$user["age"] = 31; // 把键名为age的元素30改为31
print_r($user); // 输出Array ( [name] => John [age] => 31 [country] => USA )

7. Traversing arrays

PHP provides a variety of ways to traverse arrays, including for loops, foreach loops, and while loops. Among them, the foreach loop is most commonly used when processing arrays.

// for循环遍历普通数组
$arr = ["a", "b", "c"];
for ($i = 0; $i < count($arr); $i++) {
    echo $arr[$i] . "
";
} // 输出a b c
 
// foreach循环遍历普通数组
$arr = ["a", "b", "c"];
foreach ($arr as $value) {
    echo $value . "
";
} // 输出a b c
 
// foreach循环遍历关联数组
$user = ["name" => "John", "age" => 30, "country" => "USA"];
foreach ($user as $key => $value) {
    echo $key . ": " . $value . "
";
} // 输出name: John age: 30 country: USA

The above are the common methods of PHP arrays. Mastering these methods can better handle array type data often used in PHP applications.

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