madan，所有事情都敢赶在一起。。。以后每天中午去学车啊，好开心。。晚上好困，但是困也得啃书。。。。。。。。
二、PHP脚本编程语言
什么变量啊，数据类型啊，特别特别基本的不记录了，说点容易忽略的。
<?<span>php
</span><span>define</span>("PI", 3.1415926); <span>//</span><span>常量的定义</span><span>echo</span> "圆周率=".<span>PI</span>."<br/>"; <span>//</span><span>.的链接作用，同样用于$var的赋值等</span><span>if</span> (<span>PI</span><3&&<span>PI</span>>=2<span>) {
</span><span>$var</span>="shit"<span>;
}</span><span>else</span><span>{
</span><span>echo</span> "f**k"."<hr/>"<span>;
}
</span><span>//</span><span> 先判断PI<3，如果不成立，就直接进入else——称为短路设计，加快程序速度；
// 同理，为了实现程序的高效，把最容易出错的放前面，最复杂的计算放右边</span><span>$var</span>="asldkjflajdfklj"<span>;
</span><span>$v2</span>=(<span>boolean</span>)<span>$var</span>; <span>//</span><span>强制类型转换</span><span>echo</span><span>$v2</span>;<span>echo</span> "<br/>"<span>;
</span><span>$v_true</span>=<span>true</span>; <span>//</span><span>boolean值也可以直接赋值</span><span>if</span> (<span>is_bool</span>(<span>$v2</span>)&&<span>$v2</span>===<span>$v_true</span>) { <span>//</span><span>恒等===，可以判断数据类型是否相同；is_bool</span><span>echo</span> "Variables have the same value and type!"<span>;
</span><span>echo</span> "<hr/>"<span>;
}
</span><span>//</span><span>另外，非恒等仍然是!==</span><span>$lll</span>="dfa"+333<span>;
</span><span>var_dump</span>(<span>$lll</span>);<span>echo</span> "<hr/>"<span>;
</span><span>print_r</span>(<span>$lll</span>);<span>echo</span> "<hr/>"<span>;
</span><span>echo</span><span>gettype</span>(<span>$lll</span>);<span>echo</span> "<hr/>"<span>;
</span><span>//</span><span>var_dump允许一次检查多个变量，同时提供信息；print_r多用来对数组和对象进行输出；</span><span>if</span> (<span>isset</span>(<span>$lll</span>)&&!<span>empty</span>(<span>$v2</span>)) { <span>//</span><span>判断是否为空</span><span>unset</span>(<span>$lll</span><span>);
}
</span><span>var_dump</span>(<span>$lll</span>);<span>echo</span> "<hr/>"; <span>//</span><span>会报错，但仍能输出null</span><span>function</span> doubleint(<span>$var</span>){ <span>//</span><span>自定义函数</span><span>if</span> (<span>is_int</span>(<span>$var</span><span>)) {
</span><span>$var</span>=<span>$var</span>*2<span>;
</span><span>return</span><span>$var</span><span>;
}</span><span>else</span><span>{
</span><span>echo</span> "Please enter a int data."<span>;
}
}
</span><span>echo</span> doubleint(<span>$var</span>);<span>echo</span> "<hr/>"<span>;
</span><span>echo</span> doubleint(4);<span>echo</span> "<hr/>"<span>;
</span><span>//</span><span>个人觉得，还是少用global和地址传递，逻辑上容易出错，程序没错，结果却不对
// 关于include和require
// 多用include吧
// include失败了只是警告，后者则是错误然后中断程序
// 同时推荐没事儿就写绝对路径，好读也不易出错</span>要说的都在上面了，总结下就是：常量，连接符，自定义函数，类型转换，类型判断，文件引用，恒等符，短路设计，var_dump。
立即学习“PHP免费学习笔记（深入）”；
比较乱。
最后举个例子吧，自制乘法表
<?<span>php
</span><span>//</span><span>Chapter 2's example which is a chengfabiao</span><span>function</span> chengfabiao(<span>$var</span><span>){
</span><span>for</span> (<span>$row</span>=1;<span>$row</span><=<span>$var</span>;<span>$row</span>++<span>){
</span><span>for</span>(<span>$queue</span>=1;<span>$queue</span><=<span>$var</span>;<span>$queue</span>++<span>){
</span><span>$answer</span>=<span>$row</span>*<span>$queue</span><span>;
</span><span>echo</span> "<span>$row</span>*<span>$queue</span>=".<span>$answer</span>." "<span>;
}
</span><span>echo</span> "<hr/>"<span>;
}
}
</span><span>$var</span>=9<span>;
chengfabiao(</span><span>$var</span>);
自己改着玩吧。基础的东西也得常常拿出来温习下，我是这么认为的。
以上就介绍了PHP&MySQL（二）——困也得啃书，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。
