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一篇不错的PHP基础学习笔记_php基础

程序员文章站 2022-04-15 18:42:37
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1、 PHP片段四种表示形式。
标准tags:
short tags: ?> 需要在php.ini中设置short _open_tag=on,默认是on
asp tags: 需要在php.ini中设置asp_tags=on,默认是off
script tags:
2、 PHP变量及数据类型
1) $variable ,变量以字母、_开始,不能有空格
2) 赋值$variable=value;
3) 弱类型,直接赋值,不需要显示声明数据类型
4) 基本数据类型:Integer,Double,String,Boolean,Object(对象或类),Array(数组)
5) 特殊数据类型:Resourse(对第三方资源(如数据库)的引用),Null(空,未初始化的变量)
3、 操作符
1) 赋值操作符:=
2) 算术操作符:+,-,*,/,%(取模)
3) 连接操作符:. ,无论操作数是什么,都当成String,结果返回String
4) Combined Assignment Operators合计赋值操作符:+=,*=,/=,-=,%=,.=
5) Automatically Incrementing and Decrementing自动增减操作符:
(1)$variable+=1 $variable++;$variable-=1 $variable-,跟c语言一样,先做其他操作,后++或-
(2)++$variable,-$variable,先++或-,再做其他操作
6) 比较操作符:= =(左边等于右边),!=(左边不等于右边),= = =(左边等于右边,且数据类型相同),>=,>,7) 逻辑操作符:|| ó or,&&óand,xor(当左右两边有且只有一个是true,返回true),!
4、 注释:
单行注释:// ,#
多行注释:/* */
5、 每个语句以;号结尾,与java相同
6、 定义常量:define(“CONSTANS_NAME”,value)
7、 打印语句:print,与c语言相同
8、 流程控制语句
1) if语句:
(1)if(expression)
{
//code to excute if expression evaluates to true
}
(2)if(expression)
{
}
else
{
}
(3)if(expression1)
{
}
elseif(expression2)
{
}
else
{
}
2) swich语句
switch ( expression )
{
case result
// execute this if expression results in result1
break;
case result
// execute this if expression results in result2
break;
default:
// execute this if no break statement
// has been encountered hitherto
}
3) ?操作符:
( expression )?returned_if_expression_is_true:returned_if_expression_is_false;
4) while语句:
(1) while ( expression )
{
// do something
}
(2)do
{
// code to be executed
} while ( expression );
5) for语句:
for ( initialization expression; test expression; modification expression ) {
// code to be executed
}
6) break;continue
9、 编写函数
1) 定义函数:
function function_name($argument1,$argument2,……) //形参
{
//function code here;
}
2) 函数调用
function_name($argument1,$argument2,……); //形参
3) 动态函数调用(Dynamic Function Calls):


Listing 6.5


function sayHello() { //定义函数sayHello
print "hello
";
}
$function_holder = "sayHello"; //将函数名赋值给变量$function_holder
$function_holder(); //变量$function_holder成为函数sayHello的引用,调用$function_holder()相当于调用sayHello
?>


4) 变量作用域:
全局变量:


Listing 6.8


$life=42;
function meaningOfLife() {
global $life;
/*在此处重新声明$life为全局变量,在函数内部访问全局变量必须这样,如果在函数内改变变量的值,将在所有代码片段改变*/
print "The meaning of life is $life
";
}
meaningOfLife();
?>


5) 使用static


Listing 6.10


function numberedHeading( $txt ) {
static $num_of_calls = 0;
$num_of_calls++;
print "

$num_of_calls. $txt

";
}
numberedHeading("Widgets"); //第一次调用时,打印$num_of_calls值为1
print("We build a fine range of widgets

");
numberedHeading("Doodads"); /*第一次调用时,打印$num_of_calls值为2,因为变量是static型的,static型是常驻内存的*/
print("Finest in the world

");
?>


6) 传值(value)和传址(reference):
传值:function function_name($argument)


Listing 6.13


function addFive( $num ) {
$num += 5;
}
$orignum = 10;
addFive( &$orignum );
print( $orignum );
?>


结果:10
传址:funciton function_name(&$argument)


Listing 6.14


function addFive( &$num ) {
$num += 5; /*传递过来的是变量$num的引用,因此改变形参$num的值就是真正改变变量$orignum物理内存中保存的值*/
}
$orignum = 10;
addFive( $orignum );
print( $orignum );
?>


结果:15
7) 创建匿名函数:create_function(‘string1','string2'); create_function是PHP内建函数,专门用于创建匿名函数,接受两个string型参数,第一个是参数列表,第二个是函数的主体


Listing 6.15


$my_anon = create_function( '$a, $b', 'return $a+$b;' );
print $my_anon( 3, 9 );
// prints 12
?>


8) 判断函数是否存在:function_exists(function_name),参数为函数名
10、 用PHP连接MySQL
1) 连接:&conn=mysql_connect("localhost", "joeuser", "somepass");
2) 关闭连接:mysql_close($conn);
3) 数据库与连接建立联系:mysql_select_db(database name, connection index);
4) 将SQL语句给MySQL执行:$result = mysql_query($sql, $conn); //增删改查都是这句
5) 检索数据:返回记录数:$number_of_rows = mysql_num_rows($result);
将记录放入数组:$newArray = mysql_fetch_array($result);
例子:
// open the connection
$conn = mysql_connect("localhost", "joeuser", "somepass");
// pick the database to use
mysql_select_db("testDB",$conn);
// create the SQL statement
$sql = "SELECT * FROM testTable";
// execute the SQL statement
$result = mysql_query($sql, $conn) or die(mysql_error());
//go through each row in the result set and display data
while ($newArray = mysql_fetch_array($result)) {
// give a name to the fields
$id = $newArray['id'];
$testField = $newArray['testField'];
//echo the results onscreen
echo "The ID is $id and the text is $testField
";
}
?>
11、 接受表单元素:$_POST[表单元素名],
ó$_POST[user]
接受url中queryString中值(GET方式):$_GET[queryString]
12、转向其他页面:header("Location: http://www.samspublishing.com");
13、字符串操作:
1)explode(“-”,str)óJava中的splite
2)str_replace($str1,$str2,$str3) =>$str1要查找的字符串,$str2用来替换的字符串,$str3从这个字符串开始查找替换
3)substr_replace:
14、session:
1)打开session:session_start(); //也可以在php.ini设置session_auto_start=1,不必再每个script都写这句,但是默认为0,则必须要写。
2)给session赋值:$_SESSION[session_variable_name]=$variable;
3)访问session:$variable =$_SESSION[session_variable_name];
4)销毁session:session_destroy();
15、显示分类的完整例子:
//connect to database
$conn = mysql_connect("localhost", "joeuser", "somepass")
or die(mysql_error());
mysql_select_db("testDB",$conn) or die(mysql_error());
$display_block = "

My Categories


Select a category to see its items.

";
//show categories first
$get_cats = "select id, cat_title, cat_desc from
store_categories order by cat_title";
$get_cats_res = mysql_query($get_cats) or die(mysql_error());
if (mysql_num_rows($get_cats_res) $display_block = "

Sorry, no categories to browse.

";
} else {
while ($cats = mysql_fetch_array($get_cats_res)) { //将记录放入变量$cats中
$cat_id = $cats[id];
$cat_title = strtoupper(stripslashes($cats[cat_title]));
$cat_desc = stripslashes($cats[cat_desc]);
$display_block .= "

href="$_SERVER[PHP_SELF][U1] ?cat_id=$cat_id">$cat_title//点击此url,刷新本页,第28行读取cat_id,显示相应分类的条目

$cat_desc

";
if ($_GET[cat_id] == $cat_id) { //选择一个分类,看下面的条目
//get items
$get_items = "select id, item_title, item_price
from store_items where cat_id = $cat_id
order by item_title";
$get_items_res = mysql_query($get_items) or die(mysql_error());
if (mysql_num_rows($get_items_res) $display_block = "

Sorry, no items in
this category.

";
} else {
$display_block .= "
    ";
    while ($items = mysql_fetch_array($get_items_res)) {
    $item_id = $items[id];
    $item_title = stripslashes($items[item_title]);
    $item_price = $items[item_price];
    $display_block .= "
  • href="showitem.php?item_id=$item_id">$item_title
    ($$item_price)";
    [U2] }
    $display_block .= "
";
}
}
}
}
?>


My Categories


print $display_block; ?>


16、PHP连接Access:

$dbc=new com("adodb.connection");
$dbc->open("driver=microsoft access driver (*.mdb);dbq=c:member.mdb");
$rs=$dbc->execute("select * from tablename");
$i=0;
while (!$rs->eof){
$i+=1
$fld0=$rs->fields["UserName"];
$fld0=$rs->fields["Password"];
....
echo "$fld0->value $fld1->value ....";
$rs->movenext();
}
$rs->close();
?>