


This article mainly introduces the relevant knowledge points and detailed usage of automatic loading (autoloading) of PHP files. Friends who need this can refer to it.
Traditionally, in PHP, when we want to use a class file, we have to require or include it at the head of the document:
<?php require_once('../includes/functions.php'); require_once('../includes/database.php'); require_once('../includes/user.php'); ...
But once there are too many documents to be called, you have to write one line each time, which does not look good. Is there any way to make PHP documents load automatically?
<?php function __autoload($class_name) { require "./{$class_name}.php"; }
Yes, you can use PHP’s magic function __autoload(). The above example is to automatically load the PHP file in the current directory. Of course, in practice, we are more likely to use it like this:
<?php function __autoload($class_name) { $name = strtolower($class_name); $path = "../includes/{$name}.php"; if(file_exists($path)){ require_once($path); }else{ die("the file {$class_name} could not be found"); } }
That is, we do a certain case processing of the file name, and then check it before require Whether the file exists, if not, display customized information.
Similar usage is often seen in private projects, or in the framework of a single project. Why? Because you can only define one __autoload function, in multi-person development, it is impossible for different developers to use different customized autoloaders, unless everyone has agreed in advance to use one __autoload, and any changes are involved. Version synchronization is troublesome.
Mainly because of this, the good news is that the __autoload function will soon be deprecated in version 7.2 of PHP.
Warning This feature has been DEPRECATED as of PHP 7.2.0. Relying on this feature is highly discouraged.
Then it is replaced by something called spl_autoload_register(), which has the advantage of being customizable Multiple autoloaders.
//使用匿名函数来autoload spl_autoload_register(function($class_name){ require_once('...'); });
//使用一个全局函数 function Custom() { require_once('...'); } spl_autoload_register('Custom');
//使用一个class当中的static方法 class MyCustomAutoloader { static public function myLoader($class_name) { require_once('...'); } } //传array进来,第一个是class名,第二个是方法名 spl_autoload_register(['MyCustomAutoloader','myLoader']);
//甚至也可以用在实例化的object上 class MyCustomAutoloader { public function myLoader($class_name) { } } $object = new MyCustomAutoloader; spl_autoload_register([$object,'myLoader']);
It is worth mentioning that using autoload, whether it is __autoload() or spl_autoload_register(), compared to require or include, the advantage is that the autoload mechanism is lazy loading, that is It is not that all those files are called for you as soon as you run it, but only the ones you use, such as which files are new, will the corresponding files be loaded through the autoload mechanism.
Of course, spl_autoload_register is often used in laravel including various packages, such as here:
/** * Prepend the load method to the auto-loader stack. * * @return void */ protected function prependToLoaderStack() { spl_autoload_register([$this, 'load'], true, true); }
Related recommendations:
Detailed explanation of the php skills of using mb_strpos in PHP
Detailed explanation of the method of using zlib extension to achieve GZIP compression output in PHP
The above is the detailed content of Detailed explanation of automatic loading php examples of PHP files. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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