PSR

$gorilla = newAnimalsGorilla;
$ibis = newAnimalsStrawNeckedIbis;

if ($gorilla->isWake() === true) {
    do {
        $gorilla->beatChest();
    } while ($ibis->isAsleep() === true);
    
    $ibis->flyAway();
}

$closureWithArgs = function ($arg1, $arg2) {
    //body
};

$closureWithArgsAndVars = function ($arg1, $arg2) use ($var1, $var2) {
    //body
};

<?php

namespace PsrLog;

/**
 * Describes a logger instance
 *
 * The message MUST be a string or object implementing __toString().
 *
 * The message MAY contain placeholders in the form: {foo} where foo
 * will be replaced by the context data in key "foo".
 *
 * The context array can contain arbitrary data, the only assumption that
 * can be made by implementors is that if an Exception instance is given
 * to produce a stack trace, it MUST be in a key named "exception".
 *
 * See https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-3-logger-interface.md
 * for the full interface specification.
 */
interfaceLoggerInterface
{
    /**
     * System is unusable.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function emergency($message, array $context = array());

    /**
     * Action must be taken immediately.
     *
     * Example: Entire website down, database unavailable, etc. This should
     * trigger the SMS alerts and wake you up.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function alert($message, array $context = array());

    /**
     * Critical conditions.
     *
     * Example: Application component unavailable, unexpected exception.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function critical($message, array $context = array());

    /**
     * Runtime errors that do not require immediate action but should typically
     * be logged and monitored.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function error($message, array $context = array());

    /**
     * Exceptional occurrences that are not errors.
     *
     * Example: Use of deprecated APIs, poor use of an API, undesirable things
     * that are not necessarily wrong.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function warning($message, array $context = array());

    /**
     * Normal but significant events.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function notice($message, array $context = array());

    /**
     * Interesting events.
     *
     * Example: User logs in, SQL logs.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function info($message, array $context = array());

    /**
     * Detailed debug information.
     *
     * @param string $message
     * @param array $context
     * @return void
     */
    public function debug($message, array $context = array());

    /**
     * Logs with an arbitrary level.
     *
     * @param mixed $level
     * @param string $message
     * @param array $context
     * @return void
     */
    public function log($level, $message, array $context = array());
}

/**
 * 使用SPL组册这个自动加载函数后，遇到下述代码时这个函数会尝试   从/path/to/project/src/Baz/Qux.php文件中加载FooBarBazQux类：
 *  new FooBarBazQux;
 * @param string $class 完全限定的类名。
 * @return void
 **/spl_autoload_register(function ($class) {
    //项目的命名空间前缀
    $prefix = 'Foo\Bar\';
    
    //目录前缀对应的根目录
    $base_dir = __DIR__ . '/src/';
    
    //判断传入的类是否使用了这个命名空间前缀
    $len = strlen($prefix);
    if (strncmp($prefix, $class, $len) !== 0) {
        //没有使用，交给注册的下一个自动加载器处理
        return;
    }
    
    //获取去掉前缀后的类名
    $relative_class = substr($class, $len);
    
    //把命名空间前缀替换成根目录，
    // 在去掉前缀的类名中，把命名空间分隔符替换成目录分隔符，
    // 然后在后面加上.php
    $file = $base_dir . str_replace('\', '/', $relative_class) . '.php';
    
    //如果该文件存在，就将其导入
    if (file_exists($file)) {
        require $file;
    }
});

先记着，后续再理解！