php数组常用方法

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

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

// 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

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

// 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 )

// 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 )

// 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 )

// 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