Let me introduce to you the PHP predefined variables that are often used in PHP learning. Through predefined variables, you can obtain information such as user sessions, user operating system environment, and local operating system environment.
$_SERVER['SERVER_ADDR'] The IP address of the server where the script is currently running.
$_SERVER['SERVER_NAME'] The name of the server host where the script is currently running.
$_SERVER['REQUEST_METHOD'] The request method when accessing the page.
$_SERVER['REMOTE_ADDR'] The IP address of the user who is browsing the current page.
$_SERVER['REMOTE_HOST'] The host name of the user who is browsing the current page.
$_SERVER['REMOTE_PORT'] The port used by users to connect to the server.
$_SERVER['SCRIPT_FILENAME'] The absolute path of the currently executing script.
$_SERVER['SERVER_PORT'] The port used by the server.
$_SERVER['SERVER_SIGNATURE'] A string containing the server version and virtual host name.
$_SERVER['DOCUMENT_ROOT'] The document root directory where the currently running script is located.
$_COOKIE Information passed to the script through HTTPCookie. These are set by setcookie() when executing the php script.
$_SESSION contains information about all session variables. The $_SESSION variable is mainly used for session control and value transfer between pages.
$_POST Parameter information passed through the post method.
$_GET Parameter information passed through the get method.
$_GLOBALS An array consisting of all defined global variables. The variable name is the index into the array. It can be called a super set of all super variables.

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。


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