PHP function introduction—http_build_query()`: Build URL query string

PHP function introduction—http_build_query(): Build URL query string

In PHP development, you often encounter scenarios where you need to combine some parameters into a URL query string. In order to facilitate developers to process these parameters and convert them into strings that comply with URL specifications, PHP provides the http_build_query() function.

Function introduction
http_build_query() function is a very practical function. Its function is to convert an associative array or object into a URL query string. This function can automatically convert the key-value pairs of an array or object into a string that conforms to the URL specification and connect them with the "&" symbol.

Code Example
The following is a code example that shows how to use the http_build_query() function:

<?php
$params = [
    'name' => 'John',
    'age' => 25,
    'city' => 'New York'
];

$queryString = http_build_query($params);
echo $queryString;
?>

The output is:

name=John&age=25&city=New+York

In the above example, We define an associative array $params, which contains three parameters: name, age and city. We then use the http_build_query() function to convert the $params array into a URL query string and assign the result to the $queryString variable. Finally, we use the echo statement to output the value of $queryString.

Parameter processing
http_build_query() function can also handle complex parameter structures. For example, it can handle multidimensional arrays, objects, and special characters.

Multidimensional array
If the $params array is a multidimensional array, the http_build_query() function will automatically convert it into a string that conforms to the URL specification.

<?php
$params = [
    'name' => 'John',
    'age' => 25,
    'city' => 'New York',
    'hobbies' => [
        'reading',
        'swimming',
        'traveling'
    ]
];

$queryString = http_build_query($params);
echo $queryString;
?>

The output result is:

name=John&age=25&city=New+York&hobbies%5B0%5D=reading&hobbies%5B1%5D=swimming&hobbies%5B2%5D=traveling

In the above example, we added an element named hobbies to the $params array, whose value is an array containing three hobbies. When we use the http_build_query() function to convert the $params array into a URL query string, we will find that the hobbies parameter is converted into the form of hobbies=reading&hobbies[1]=swimming&hobbies[2]=traveling.

Object
Similarly, the http_build_query() function can also handle objects. The function automatically converts the object's public property key-value pairs into a URL query string.

<?php
class Person {
    public $name = 'John';
    public $age = 25;
    public $city = 'New York';
}

$person = new Person();
$queryString = http_build_query($person);
echo $queryString;
?>

The output result is:

name=John&age=25&city=New+York

In the above example, we define a class named Person and define three public properties in the class: name, age and city . We then created a Person object and passed it to the http_build_query() function, which converted the object's properties into a URL query string.

Special characters
When the parameters contain special characters, the http_build_query() function will automatically escape them to comply with URL specifications.

<?php
$params = [
    'name' => 'John Doe',
    'age' => 25,
    'city' => 'New York'
];

$queryString = http_build_query($params);
echo $queryString;
?>

The output is:

name=John+Doe&age=25&city=New+York

In the above example, our name parameter contains spaces. When using the http_build_query() function to convert the $params array into a URL query string, the function converts spaces into plus signs.

Summary
http_build_query() function is a very practical function in PHP. It can help developers quickly and easily convert an associative array or object into a URL query string. Whether it is a simple parameter list or a complex multi-dimensional array or object, the http_build_query() function can handle it. By properly using the http_build_query() function, we can process URL parameters more efficiently and improve the readability and maintainability of the code.

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