w3school的PHP教程提炼（一）PHP基础
本笔记只提炼php需要注意的部分，关于运算符，简单判断等内容一概不写。
1 字符串
1.1 strlen()函数计算字符串长度
<p class="sycode"> <? php echo strlen ( " hello world! " ); ?> </p>
1.2 strops()函数在字符串内检索字符串或字符
<p class="sycode"> <? php echo strpos ( " hello world " , " world " ); ?> </p>
2 数组
2.1 数值数组 带有数字ID键的数组
自动分配ID键：
<p class="sycode"> $names = array ( " a " , " b " , " c " ); </p>
人工分配ID键：
<p class="sycode"> $names [ 0 ] = " a " ; $names [ 1 ] = " b " ; $names [ 2 ] = " c " ; </p>
使用ID键：
<p class="sycode"> <? php echo $names [ 0 ] . " & " . $names [ 1 ] . " & " . $names [ 2 ]; ?> </p>
2.2 关联数组 数组中的每个ID键关联一个值
将值作为键分配：
<p class="sycode"> $ages = array ( " a " => 10 , " b " => 20 , " c " => 30 ); </p>
另一种方法：
<p class="sycode"> $ages [ " a " ] = " 10 " ; $ages [ " b " ] = " 20 " ; $ages [ " c " ] = " 30 " ; </p>
使用ID键：
<p class="sycode"> <? php echo " a is " . $ages [ " a " ] . " years old. " ; ?> </p>
2.3 多维数组 包含一个或多个数组的数组（略）
3 循环
3.1 while
<p class="sycode"> <? php $i = 1 ; while ( $i <= 5 ){ echo " the number is " . $i . " <br /> " $i ++ ;} ?> </p>
3.2 do...while
<p class="sycode"> <? php $i = 0 ; do { $i ++ ; echo " the number is " . $i . " <br /> " ;} while ( $i < 5 ); ?> </p>
3.3 for
<p class="sycode"> <? php for ( $i = 1 ; $i <= 5 ; $i ++ ){ echo " hello world!<br /> " ;} ?> </p>
3.4 foreach
foreach语句用于循环遍历数组，每进行一次循环，当前数组元素的值就会被赋值给value变量（数组指针会逐一地移动）以此类推。
语法
<p class="sycode"> foreach ( array as value){ // ... } </p>示例：输出给定数组的值
<p class="sycode"> <? php $arr = array ( " one " , " two " , " three " ); foreach ( $arr as $value ){ echo " value: " . $value . " <br /> " ;} ?> </p>
4 函数
4.1 传递参数
<p class="sycode"> <? php function writeName( $firstname , $lastname ){ echo $firstname . $lastname . " <br /> " ;} echo " my name is " ;writeName( " Gang " , " Li " ); echo " my name is " writeName( " San " , " Zhang " ); ?> </p>
4.2 返回值
<p class="sycode"> <? php function add( $x , $y ){ $total = $x + $y ; return $total ;} echo " 1 + 2 = " . add( 1 , 2 ); // print 1 + 2 = 3 ?> </p>
5 表单处理
$_GET变量用于收集来自method="get"的表单的值。
$_POST变量用于收集来自method="post"的表单的值。
5.1 $_GET变量
form.php
<p class="sycode"> < form action ="welcome.php" method ="get" > Name: < input type ="text" name ="name" /> Age: < input type ="text" name ="age" /> < input type ="submit" /> </ form > </p>
welcome.php
<p class="sycode"> Welcome <? php echo $_GET [ " name " ]; ?>.< br /> You are <? php echo $_GET [ " age " ]; ?> years old ! </p>
5.2 $_POST变量
与$_GET不同之处在于：
$_POST没有发送信息量限制，而$_GET限制100字符
$_POST不在url处体现表单中的值，而$_GET传递的url可以加入收藏夹
5.3 $_REQUEST变量
$_REQUEST变量可用来取得通过get和post方法发送到表单数据的结果
