Foreword: Around 2006, I studied PHP for a period of time, and made a download website at that time. Later, because I used Java and j2ee during my graduate studies, I dropped PHP. A lot of changes have taken place over the years, the biggest one being support for object-oriented programming.
Now because I need to do something with php, I have to learn it again and start from scratch!
Difference between echo and print:
To set a constant, use the define() function - it takes three arguments:
<?php define("GREETING", "Welcome to W3School.com.cn!"); echo GREETING; ?>
运算符 | 名称 | 例子 | 结果 |
---|---|---|---|
== | 等于 | $x == $y | 如果 $x 等于 $y,则返回 true。 |
=== | 全等(完全相同) | $x === $y | 如果 $x 等于 $y,且它们类型相同,则返回 true。 |
!= | 不等于 | $x != $y | 如果 $x 不等于 $y,则返回 true。 |
不等于 | $x $y | 如果 $x 不等于 $y,则返回 true。 | |
!== | 不全等(完全不同) | $x !== $y | 如果 $x 不等于 $y,且它们类型不相同,则返回 true。 |
> | 大于 | $x > $y | 如果 $x 大于 $y,则返回 true。 |
大于 | $x | 如果 $x 小于 $y,则返回 true。 | |
>= | 大于或等于 | $x >= $y | 如果 $x 大于或者等于 $y,则返回 true. |
小于或等于 | $x | 如果 $x 小于或者等于 $y,则返回 true。 |
Several predefined variables in PHP are "superglobals", which means that they are always accessible, regardless of scope - and you can access them from any function, class or file without having to do anything special.
The PHP superglobal variables are:
Element/Code | Description |
---|---|
$_SERVER['PHP_SELF'] | Returns the filename of the currently executing script |
$_SERVER['GATEWAY_INTERFACE'] | Returns the version of the Common Gateway Interface (CGI) the server is using |
$_SERVER['SERVER_ADDR'] | Returns the IP address of the host server |
$_SERVER['SERVER_NAME'] | Returns the name of the host server (such as www.w3schools.com) |
$_SERVER['SERVER_SOFTWARE'] | Returns the server identification string (such as Apache/2.2.24) |
$_SERVER['SERVER_PROTOCOL'] | Returns the name and revision of the information protocol (such as HTTP/1.1) |
$_SERVER['REQUEST_METHOD'] | Returns the request method used to access the page (such as POST) |
$_SERVER['REQUEST_TIME'] | Returns the timestamp of the start of the request (such as 1377687496) |
$_SERVER['QUERY_STRING'] | Returns the query string if the page is accessed via a query string |
$_SERVER['HTTP_ACCEPT'] | Returns the Accept header from the current request |
$_SERVER['HTTP_ACCEPT_CHARSET'] | Returns the Accept_Charset header from the current request (such as utf-8,ISO-8859-1) |
$_SERVER['HTTP_HOST'] | Returns the Host header from the current request |
$_SERVER['HTTP_REFERER'] | Returns the complete URL of the current page (not reliable because not all user-agents support it) |
$_SERVER['HTTPS'] | Is the script queried through a secure HTTP protocol |
$_SERVER['REMOTE_ADDR'] | Returns the IP address from where the user is viewing the current page |
$_SERVER['REMOTE_HOST'] | Returns the Host name from where the user is viewing the current page |
$_SERVER['REMOTE_PORT'] | Returns the port being used on the user's machine to communicate with the web server |
$_SERVER['SCRIPT_FILENAME'] | Returns the absolute pathname of the currently executing script |
$_SERVER['SERVER_ADMIN'] | Returns the value given to the SERVER_ADMIN directive in the web server configuration file (if your script runs on a virtual host, it will be the value defined for that virtual host) (such as someone@w3schools.com) |
$_SERVER['SERVER_PORT'] | Returns the port on the server machine being used by the web server for communication (such as 80) |
$_SERVER['SERVER_SIGNATURE'] | Returns the server version and virtual host name which are added to server-generated pages |
$_SERVER['PATH_TRANSLATED'] | Returns the file system based path to the current script |
$_SERVER['SCRIPT_NAME'] | Returns the path of the current script |
$_SERVER['SCRIPT_URI'] | Returns the URI of the current page |
PHP $_POST is widely used to collect form data after submitting an HTML form with method="post". $_POST is also widely used to pass variables.