How to output array in php

In PHP, an array is a very basic and important data structure that can store a series of ordered values ​​and access individual elements through subscripts. There are many types of arrays in PHP, such as index arrays, associative arrays, etc. Each type has a corresponding output method.

1. Output of index array

The index array is the most common array type in PHP. Its elements are arranged according to numerical index, starting from 0 and increasing. To output the index array, you can use a normal loop method or a foreach loop. The example is as follows:

// 定义一个索引数组
$arr = array('apple', 'banana', 'orange');

// 普通循环输出
for ($i = 0; $i < count($arr); $i++) {
    echo $arr[$i], &#39;<br>';
}

// foreach 循环输出
foreach ($arr as $item) {
    echo $item, '<br>';
}

In the above code, the first example uses a normal loop to traverse each element in the array and output it by index. The second example uses a foreach loop to assign each element to the variable $item and output it. As you can see, no matter which method is used, the elements in the array will eventually be output.

2. Output of associative array

Associative array is another common array type in PHP. Its elements are stored in the form of key-value pairs. Different from the index array, the subscript of the associative array can be a string or a number, for example:

// 定义一个关联数组
$arr = array('name' => 'Tom', 'age' => 18, 'gender' => 'male');

In the array defined above, 'name', 'age' and 'gender' are all keys of the array ( key), and the corresponding values ​​are 'Tom', 18 and 'male'.

The method of outputting associative arrays is similar to outputting index arrays, and can use ordinary loops or foreach loops. It should be noted that since the subscript of an associative array is a string, numeric indexes such as $i cannot be used in ordinary loops, but key names need to be used to access the corresponding values. An example is as follows:

// 普通循环输出
foreach ($arr as $key => $value) {
    echo $key . ':' . $value . '<br>';
}

// foreach 循环输出
foreach ($arr as $value) {
    echo $value . '<br>';
}

In the above code, the first example uses foreach to loop through each key-value pair in the array and output the key name and corresponding value. The second example only outputs the values ​​in the array, because when no key name is specified in the foreach loop, only the values ​​in the array are accessed by default.

In addition to ordinary loops and foreach loops, PHP also provides some convenient functions to quickly output the values ​​in the array, such as var_dump, print_r and json_encode. These functions can output the array to the screen in a clearer way, making it easier for us to debug and view. For example:

// 使用 var_dump 输出数组
var_dump($arr);

// 使用 print_r 输出数组
print_r($arr);

// 使用 json_encode 输出数组
echo json_encode($arr);

Through these functions, we can clearly see the type, size and specific key value of each element in the array, as well as the hierarchical structure of the array and other information.

In PHP, there are many ways to output arrays, and you can choose according to different needs. Regardless of whether you use a normal loop, foreach loop, var_dump or print_r, you can easily output the elements in the array to the screen, which facilitates debugging and viewing and improves development efficiency.

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