php: The difference between require_once and require
Difference:
require_once will only load the same file once, while require will load it multiple times.
I believe that novices like me still have some doubts. So we guessed: If 456.php introduced 123.php, now the file test_require.php introduces "456.php" and "123.php". If the require method is used, then in test_require.php, 123.php will be introduced twice, and using the require_once method 123.php will be introduced once. So let’s do the experiment!
1. require method
The content of 123.php is as follows:
<?php echo "123\n";
The content of 456.php is as follows:
##
<?php
<span style="white-space:pre"> </span>require("123.php");
<span style="white-space:pre"> </span>echo "456\n";<?php
require("123.php");
require("456.php");
2. require_once method
123.php content remains unchanged. 456.php and test_require.php change the require_once method. The content is as follows:
##//456.php
<?php
require_once "123.php";
echo "456\n";
//test_require.php
<?php
require_once "123.php";
require_once "456.php";
If the require method is used in 456.php and the require_once method is used, then require_once will be invalid. The codes of the three files are as follows:
The above is the detailed content of php: The difference between require_once and require. For more information, please follow other related articles on the PHP Chinese website!//123.php
<?php
echo "123\n";
//456.php
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