PHP require
Summary: in this tutorial, you will learn how to use the PHP require construct to load the code from a file into the current script.
Introduction to the PHP require construct
PHP require
construct loads the code from an file into a script and executes that code. The following shows the syntax of the require
construct:
require 'path_to_file';
Code language: HTML, XML (xml)
To load the code from a file, you specify the file path after the require
keyword. When loading the file, the require
construct executes the code in the loaded file.
The require
construct is the same as the include
construct except that if it fails to load the file, it’ll issue a fatal error and halt the script, whereas the include
construct only issues a warning and allows the script to continue.
In practice, you often use the require
construct to load the code from libraries. Since the libraries contain the required functions to execute the script, it’s better to use the require
construct than the include
construct.
PHP require example
Suppose that you have index.php
and functions.php
, and you want to load the functions.php
to the index.php
file.
The functions.php
file has one function called dd()
, which stands for the dump and die because it uses both var_dump()
and die()
functions:
if (!function_exists('d')) {
function dd($data)
{
echo '<pre>';
var_dump($data);
echo '</pre>';
die();
}
}
Code language: HTML, XML (xml)
The index.php will look like this:
require 'functions.php';
dd([1, 2, 3]);
Code language: HTML, XML (xml)
In this file, we use the require
construct to load the code in functions.php
that defines the dd()
function if the function doesn’t exist. Then, we use dd()
function defined in the functions.php
.
PHP require is not a function
Sometimes, you see the following code:
require('functions.php');
Code language: HTML, XML (xml)
The code looks like a function call because of the parentheses ()
. and it works.
However, the parentheses are not a part of the require
construct. Instead, they belong to the file path expression that is being loaded.
PHP require_once
PHP require_once
is the counterpart of the include_once
except that the require_once issues an error if it fails to load the file. Also, the require_once
won’t load the file again if the file has been loaded.
Here’s the syntax of require_once construct:
require_once 'path_to_file';
Code language: HTML, XML (xml)
Summary
- Use
require
construct to load the code from another file into the script. - Use
require_once
construct to load the code from another file once and won’t include the file again if the file has been loaded. - The
require
andrequire_once
are language constructs, not functions.