php学习笔记（一）
1.执行运算符是反引号 (``), 相当于 shell_exec() 函数，执行一个系统命令 $out=`dir`;//列出当前的目录和文件信息 2.定义常量 define(str,this is a const variableBR);echo str; 3.字符串 用单引号或双引号括起来。区别是在双引号中出现变量时会替换为变量
1.执行运算符是反引号(``),相当于shell_exec()函数，执行一个系统命令
$out=`dir`;//列出当前的目录和文件信息
2.定义常量
define("str","this is a const variable<br>");
echo str;3.字符串
用单引号或双引号括起来。区别是在双引号中出现变量时会替换为变量的值。
$a=10;
echo("variable is $a");
echo('variable is $a');
//结果为：variable is 10variable is $a 4、接受数据
使用变量$_POST读取表单数据。如果控件的name属性为c1，则用下面的方式获取他的值：
$_POST[`c1`]
Index.php文件
ShowInfo.php文件
if(isset($_POST['submit']) && $_POST['submit']){
echo("<br>用户名：".$_POST['username']."<br>");
}5、接受网址中的参数信息
在网址中传递参数，格式为：
http://网址/网页文件?参数1>=
接受参数：使用变量：$_GET['参数名']
<a href="ShowInfo.php?name=Johney&sex=man">submit</a>
ShowInfo.php文件
echo ("name: ".$_GET['name']."<br>");
echo ("sex: ".$_GET['sex']);6、定义数组
array([key=>]value
,...
)
关键字可以是整数和字符串。关键字省略后以下一个数字为关键字，从0开始。
$arr=array("first"=>"Cpu","disk",2=>"memory","screen");
print_r($arr);
//结果：
Array ( [first] => Cpu [0] => disk [2] => memory [3] => screen )
多维数组
$arr[0][0]="CPU"; $arr[2][3]="memory"; print_r($arr); //结果： Array ( [0] => Array ( [0] => CPU ) [2] => Array ( [3] => memory ) )
7、数组函数
print_r($arr);//输出数组
$tmp=array_change_key_case($arr,CASE_LOWER);//OR CASE_UPPER
返回字符串关键字名全为小写或大写的数组
$tmp=array_count_values($arr);
统计数组中所有value出现的次数，结果返回到另一个数组中
array_fill：使用指定的值填充数组
array_fill(int start_index, int num, value);
$arr=array_fill(2,2,"element"); print_r($arr); 结果为：Array ( [2] => element [3] => element )
bool array_key_exists(key, $arr);//检查数组中指定的关键字是否存在
$tmp=array_keys($arr [,value]);//返回一个数组，列出所有关键字；若指定value，则只返回值为value的关键字
$tmp=array_merge($arr1,$arr2,...);//将多个数组合并，若关键字相同，前面的将被覆盖
array_pop($arr);//将数组的最后一个元素弹出
array_push($arr,value1,value2,...);//将多个元素压入数组尾部，数字作为关键字
array_reverse($arr);//数组反序排列
$tmp=array_sum($arr);//元素求和
array_unique($arr);//删除数组中重复的元素
arsort($arr);//降序排序
asort($arr);//升序排序
8、遍历数组
$arr=array('a'=>'a','b'=>'b','c'=>'c',"CPU","memory",'4');
foreach($arr as $val){
echo $val." ";
}
//OR:
for($i=0;$i<sizeof echo current next><br>
<p><span>两种方法效果相同，结果为：a b c CPU memory 4 </span></p>
<p><span><strong>sizeof($arr)</strong><span>获取数组元素数量，</span><span><strong>next($arr)</strong></span><span>函数将指针移动到下一个位置，</span><span><strong>current($arr)</strong></span><span>获得当前指针下的元素。</span></span></p>
<p><span>9、变长参数列表</span></p>
<p><span>在定义函数时，不指定参数。在函数体内通过以下<span>3</span><span>个函数获得参数信息：</span></span></p>
<p><span><strong>func_num_args()</strong><span><strong>：</strong>返回参数数量</span></span></p>
<p><span><strong>func_get_arg($i)</strong><span><strong>：</strong>返回下标为</span><span>i</span><span>的参数</span></span></p>
<p><span><strong>func_get_args()</strong><span><strong>：</strong>返回参数数组</span></span></p>
<p><span> </span></p>
<pre class="brush:php;toolbar:false">function sum(){
$num=func_num_args();
$sum=0;
for($i=0;$i";
}
或者：
function sum(){
$num=func_num_args();
$sum=0;
$arg_list=func_get_args();
for($i=0;$i";
}<span> </span>
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