PHP数组操作方法及常见问题解决方案

$fruits = array("apple", "banana", "cherry");

$fruits = [];
$fruits[] = "apple";
$fruits[] = "banana";
$fruits[] = "cherry";

$fruits = array("apple", "banana", "cherry");
echo $fruits[1];

$fruits = array("apple", "banana", "cherry");
$fruits[] = "orange";
print_r($fruits);

$fruits = array("apple", "banana", "cherry");
array_push($fruits, "orange");
print_r($fruits);

$fruits = array("apple", "banana", "cherry");
unset($fruits[1]); // 删除"banana"元素
print_r($fruits);

$fruits = array("apple", "banana", "cherry");
array_splice($fruits, 1, 1); // 删除"banana"元素
print_r($fruits);

$fruits = array("apple", "banana", "cherry");
for ($i = 0; $i < count($fruits); $i++) {
    echo $fruits[$i] . "<br>";
}

$fruits = array("apple", "banana", "cherry");
foreach ($fruits as $fruit) {
    echo $fruit . "<br>";
}

$arr = array();
if (empty($arr)) {
    echo "数组为空";
}
if (count($arr) == 0) {
    echo "数组为空";
}

$arr = array("name"=>"Tom", "age"=>18);
if (array_key_exists("name", $arr)) {
    echo "键名为name存在";
}
if (isset($arr["age"])) {
    echo "键名为age存在";
}

$arr = array("name"=>"Tom", "age"=>18);
echo json_encode($arr);

$json = '{"name":"Tom","age":18}';
$arr = json_decode($json, true);
print_r($arr);