php set array mode

PHP is a server-side scripting language that is widely used in Web server-side programming. In PHP, array is an important data structure. We can create and operate arrays in many ways. This article will introduce one of them: setting the array through key-value pairs.

1. Create an array

1. Use [] or array() directly to create an empty array:

$a = [];
$b = array();

2. At the same time when creating To set array elements, you can use subscripts or key-value pairs:

$a = [1, 2, 3];
$b = ['name' => '张三', 'age' => 20];

3. Array elements do not have to be set in order, and the subscripts can also be strings:

$a = [1, 'name' => '张三', 2, 'age' => 20];

2. Set the array elements

1. Set by subscript:

$a = [];
$a[0] = 1;
$a[1] = 'hello';
$a[2] = ['a' => 1, 'b' => 2];

2. Set by key-value pair:

$a = ['name' => '张三', 'age' => 20];
$a['address'] = '北京市朝阳区';

3. Set through special key-value pairs:

$a = [];
$a[] = 1; // 等价于 $a[0] = 1;
$a[] = 'hello'; // 等价于 $a[1] = 'hello';
$a['name'] = '张三'; // 等价于 $a['name'] = '张三';

3. Access array elements

1. Access through subscripts:

$a = [1, 'hello', ['a' => 1, 'b' => 2]];
echo $a[0]; // 输出1
echo $a[1]; // 输出hello
echo $a[2]['a']; // 输出1

2. Access through key-value pairs:

$a = ['name' => '张三', 'age' => 20];
echo $a['name']; // 输出张三
echo $a['age']; // 输出20

4. Traverse the array elements

1. Use a for loop to traverse:

$a = [1, 2, 3];
for ($i = 0; $i < count($a); $i++) {
    echo $a[$i], ' ';
    // 输出：1 2 3
}

2. Use a foreach loop to traverse:

$a = ['name' => '张三', 'age' => 20];
foreach ($a as $key => $value) {
    echo $key, ': ', $value, PHP_EOL;
    // 输出：name: 张三，age: 20
}

3. Use a while loop to traverse:

$a = [1, 2, 3];
while (list($key, $value) = each($a)) {
    echo $key, ': ', $value, PHP_EOL;
    // 输出：0: 1，1: 2，2: 3
}

The above is the relevant content of setting the array through key-value pairs. I hope to be helpful. PHP provides a variety of ways to create and operate arrays. Only by mastering them can you better write efficient PHP programs.

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