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HomeBackend DevelopmentPHP Tutorial这回真的是挤时间了-PHP基础(3)

这回真的是挤时间了-PHP基础(三)

  hi

刚看了唐人街探案,5星好评啊亲。由于是早就约好的,也不好推辞(虽然是和男的..),但该写的还是得挤时间写。明天早上老师的项目结题,虽然和我关系不大,但不要添乱就好!!

1、PHP 

一、PHP基础(三)
1.3.2 Int

整型。

几个点:进制问题(2,8,16);

溢出——溢出后自动转为float型;

整除;

float转为int——向下取整;

例子给出

$shi=123;
$bin=0b100001;
$ba=0123;
$shiliu=0x1234555;

function show($a){
echo "Truth is:";
var_dump($a);
echo "
";
}

show($shiliu);
show($ba);
show($bin);

$qiguaideba=01237823; //八进制的“溢出”,会截断,只输出01237

show($qiguaideba);

function zhengchu($a,$b){
$c=$a/$b;
if(is_float($c)){
var_dump(round($c)); //用round控制输出结果
}else{
var_dump($c);
}
}

zhengchu($shiliu , $ba);

1.3.3 float

php版本不同,浮点型的精确度似乎是有变化的;而且坑爹的是,由于PHP内部机制的问题,也许会出现:

var_dump(floor((0.1+0.7)*10));

返回的往往是7而不是期望中的8....

使用高精度的话,用gmp函数,请自行去了解...

然后真想比较的话,不妨设置一个最小值来比较:

$bijiao1=0.232342342;
$bijiao2=0.232342323;
$esp=0.000001;
if(abs($bijiao1-$bijiao2) echo "True"."
";
}else{
echo "F**k"."
";
}

1.3.4 字符串

单双引号括起来的就是了~

然后只想说一点的就是heredoc:

$str=
alsidjflja
akjsdhflkj
dfjlkj.
EOF;

echo $str;

基本就是这么个样子,但是注意,最后一行那个EOF;是必须要和分号紧紧相依的,而且分号后面必须是换行,EOF前面不能出现包括空格的一切东西;

然后heredoc还可以用在传递参数,初始化静态值等等;

当然,heredoc中也可以调用参数啊属性的什么的——把EOF看成是大大的双引号就好了。

其他的字符串相关,比如我经常用到的.做连接符什么的,比较基础,但是好用,去看一下视频就很明了。

nowdoc也是一种比较新的方式,不太熟悉,然后似乎相当于单引号。

1.4 变量

变量好用,变量灵活,变量难用——一般就是渐渐的这么认为的。

第一,PHP中不强调赋初值,不需要声明,但是推荐还是赋初值,养成好习惯;不赋初值,变量值为其类型的默认值;

第二,引用赋值要知道,$b=&$a;  只能对变量名进行操作;

第三,赋值一次更新一次:

$shit="asdf";
$s=123;

echo $shit;

$shit=$s;
echo $shit;

2、GD库实现图片水印与缩略图

一、简介

使用PHP中自带的GD库制作图片的水印。

适合大批量的图片的简单处理。

学习基本的方法,然后封装为一个工具类。 

 

这周末除了看星球大战,就来补过补过,知道错了。。。。。

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