php 基本函数

Jun 23, 2016 pm 02:31 PM

简介:这是php 基本函数 的详细页面,介绍了和php,有关的知识、技巧、经验,和一些php源码等。

class='pingjiaF' frameborder='0' src='http://biancheng.dnbcw.info/pingjia.php?id=335085' scrolling='no'> 定义常数
define('APPCONFIG','plaConfig');
获取常数
echo constant('APPCONFIG')."\n";
常数不能定义两次

初始化变量值
ini_set('display_errors',1);
获取变量值。
echo ini_get('display_errors')."\n";


用PHP的
ob_start();

相关函数简介:
1、Flush:刷新缓冲区的内容,输出。
函数格式:flush()
说明:这个函数经常使用,效率很高。
2、ob_start :打开输出缓冲区
函数格式:void ob_start(void)
说明:当缓冲区激活时,所有来自PHP程序的非文件头信息均不会发送,而是保存在内部缓冲区。为了输出缓冲区的内容,可以使用ob_end_flush()或flush()输出缓冲区的内容。
3 、ob_get_contents :返回内部缓冲区的内容。
使用方法:string ob_get_contents(void)
说明:这个函数会返回当前缓冲区中的内容,如果输出缓冲区没有激活,则返回 FALSE 。
4、ob_get_length:返回内部缓冲区的长度。
使用方法:int ob_get_length(void)
说明:这个函数会返回当前缓冲区中的长度;和ob_get_contents一样,如果输出缓冲区没有激活。则返回 FALSE。
5、ob_end_flush :发送内部缓冲区的内容到浏览器,并且关闭输出缓冲区。
使用方法:void ob_end_flush(void)
说明:这个函数发送输出缓冲区的内容(如果有的话)。
6、ob_end_clean:删除内部缓冲区的内容,并且关闭内部缓冲区
使用方法:void ob_end_clean(void)
说明:这个函数不会输出内部缓冲区的内容而是把它删除!
7、ob_implicit_flush:打开或关闭绝对刷新
使用方法:void ob_implicit_flush ([int flag])
说明:使用过Perl的人都知道$|=x的意义,这个字符串可以打开/关闭缓冲区,而ob_implicit_flush函数也和那个一样,默认为关闭缓冲区,打开绝对输出后,每个脚本输出都直接发送到浏览器,不再需要调用 flush()


例子:

php
ob_start();
echo "hello\n";
$c=ob_get_contents();
ob_end_flush();
echo "cache=".$c;
?>

输出:
hello
cache=hello



$t0=0;
$s0=0;
$t1=0;
$s1=0;
$t2=0;
$s2=0;
$t3=0;
$s3=0;
if (ob_get_level()){
$t0=1;
$s0=ob_get_level();
}
ob_start();
if (ob_get_level()){
$t1=1;
$s1=ob_get_level();
}
ob_start();
if (ob_get_level()){
$t2=1;
$s2=ob_get_level();
}
ob_start();

if ( ob_get_level()){
$t3=1;
$s3=ob_get_level();
}
ob_end_flush();
ob_end_flush();
ob_end_flush();
echo "t0=".$t0."\n";
echo "s0=".$s0."\n";
echo "t1=".$t1."\n";
echo "s1=".$s1."\n";
echo "t2=".$t2."\n";
echo "s2=".$s2."\n";
echo "t3=".$t3."\n";
echo "s3=".$s3."\n";


输出:
t0=0
s0=0
t1=1
s1=1
t2=1
s2=2
t3=1
s3=3

die( )
函数输出一条消息,并退出当前脚本。

该函数是 exit() 函数的别名。
语法

die(status)

参数 描述
status 必需。规定在退出脚本之前写入的消息或状态号。状态号不会被写入输出。
说明

如果 status 是字符串,则该函数会在退出前输出字符串。

如果 status 是整数,这个值会被用作退出状态。退出状态的值在 0 至 254 之间。退出状态 255 由 PHP 保留,不会被使用。状态 0 用于成功地终止程序。


file_exists()
文件是否存在,
is_readable()
文件是否可读
realpath()
绝对路径

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