zoukankan      html  css  js  c++  java
  • php != 和 !== 的区别

    == and != do not take into account the data type of the variables you compare. So these would all return true:

    '0'   == 0
    false == 0
    NULL  == false

    === and !== do take into account the data type. That means comparing a string to a boolean willnever be true because they're of different types for example. These will all return false:

    '0'   === 0
    false === 0
    NULL  === false

    You should compare data types for functions that return values that could possibly be of ambiguous truthy/falsy value. A well-known example is strpos():

    // This returns 0 because F exists as the first character, but as my above example,
    // 0 could mean false, so using == or != would return an incorrect result
    var_dump(strpos('Foo', 'F') != false);  // bool(false)
    var_dump(strpos('Foo', 'F') !== false); // bool(true), it exists so false isn't returned

    转自: http://stackoverflow.com/questions/3641819/php-not-equal-to-and
  • 相关阅读:
    idea--不能启动问题
    linux--mysql5.7安装
    vmware
    debezium
    java枚举
    springfox
    日志级别
    lombok--知识点
    es6--箭头函数
    网址访问过慢
  • 原文地址:https://www.cnblogs.com/pinganzi/p/5553987.html
Copyright © 2011-2022 走看看