Conversion of php multidimensional array and json format

PHP is a multi-purpose, open source scripting language that is very suitable for programming for web development needs. Multidimensional arrays and JSON format are also two very important concepts in web development. They are often used to save and transfer data. This article will introduce in detail how to convert multi-dimensional arrays and JSON formats in PHP.

1. Multidimensional array

Multidimensional array refers to an array containing multiple arrays as elements. Each array itself can also be a multidimensional array. Its structure can be viewed as a tree shape:

array(
    array( 1, 2, 3),
    array( 4, 5, 6),
    array( 7, 8, 9)
)

where each element in the array is an array with its own index and elements.

In PHP, you can use arrays as a data structure. Common operations include adding elements, modifying elements, finding elements, deleting elements, traversing arrays, etc. The following are some common operations:

1. Add elements

Use [] or array_push() function to add elements to the array:

$arr = array();
$arr[] = "apple";
$arr[] = "banana";
$arr[] = "orange";
array_push($arr, "pear");

2. Modify elements

Use the subscript operation to modify the element value in the array:

$arr = array("apple", "banana", "orange");
$arr[1] = "pear";

3. Find the element

Use the in_array() function to determine whether the element exists in the array:

$arr = array("apple", "banana", "orange");
if(in_array("banana", $arr)){
    echo "exist";
}

4. Delete elements

Use the unset() function to delete elements in the array:

$arr = array("apple", "banana", "orange");
unset($arr[1]);

5. Traverse the array

Use the foreach() function You can traverse the elements in the array:

$arr = array("apple", "banana", "orange");
foreach($arr as $item){
    echo $item;
}

2. JSON format

JSON (JavaScript Object Notation) is a lightweight data exchange format based on a subset of the JavaScript language. Use simple and easy-to-read text to describe data objects, often used for data transmission between web applications and servers.

JSON consists of two data structures: name/value pairs and value lists. A name/value pair represents a key-value pair, where the name is of type string and the value can be a string, number, boolean, array, or another set of name/value pairs. A value list consists of an ordered sequence of values ​​with no names between elements and contains only a single value. Use commas to separate different values ​​or key-value pairs in JSON.

In PHP, you can easily convert JSON strings into arrays or objects, and you can also convert PHP arrays or objects into JSON strings.

1. Convert JSON string into array

Use json_decode() function to convert JSON string into PHP array:

$json_str = '{"name":"John", "age":"30", "city":"New York"}';
$arr = json_decode($json_str, true);

The second parameter is true Indicates returning an associative array. If this parameter is not passed, the object will be returned by default.

2. Convert PHP array into JSON string

Use json_encode() function to convert PHP array into JSON string:

$arr = array("name"=>"John", "age"=>"30", "city"=>"New York");
$json_str = json_encode($arr);

3. PHP multi-dimensional array and JSON format conversion

1. Convert multi-dimensional arrays into JSON strings

Use the json_encode() function to convert multi-dimensional arrays into JSON strings. The sample code is as follows:

$arr = array(
    "name"=>array("first"=>"John", "last"=>"Smith"),
    "age"=>30,
    "city"=>"New York"
);
$json_str = json_encode($arr);

2. Convert JSON string into multi-dimensional array

Use json_decode() function to convert JSON string into multi-dimensional array. The sample code is as follows:

$json_str = '{"name":{"first":"John","last":"Smith"},"age":30,"city":"New York"}';
$arr = json_decode($json_str, true);

The above is the difference between PHP multi-dimensional array and Regarding the JSON format conversion method, readers can choose the appropriate method according to their own needs. In actual development, the conversion of multi-dimensional arrays and JSON formats is often involved, so these knowledge points are very important for web developers.

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