Abandoned fish--how long does PHP take to get from getting started to giving up? 12

Today's Lesson: PHP 3-Day Foundation Consolidation video Tutorial "Yan 18"

1. Super Global variables

/*$_SESSION$_COOKIE$_FILES$_ENV//server operating system environment variables. such as the operating system; type, Linux, win, MAC, environment variables, etc. $_server//$GLOBALS//The alias of the global variable roster, you can change the amount of arbitrary access to the global variable */print_r ($_ENW);//easily expose the server information, Print_r ($_server) is not generally allowed;//Gets the domain name of the current Web site and the currently accessed script, visitor IP (remote_addr,http_x_forward_for)//print_r ($_files); echo " <br/> "; $a = 3; $b = 4;function T () {print_r ($GLOBALS); $GLOBALS [' a '] = 99;} T (); Echo $a;

2. Constants

echo "<br/>";//constant: Post-declaration value cannot be modified//Declare a constant define (' pi ', 3.14);//The constant name is not added $echo PI, ' <br/> ';//naming specification: Same as variable, just used to all uppercase Features: The post-declaration value cannot be modified or destroyed, can be accessed anywhere on the page/*pi = 3.15;echo pi;define (' pi ', 3.15); unset (pi); */echo "<br/>"; function A () { echo PI;} A (); echo "<br/>";//Detect constant if (defined (' PI ')) {echo "constant exists";} Formally developed generally such if (!defined (' GEI ')) {define (' GEI ', 8846);} echo Gei;echo "<br/>";//dynamic variable name, use variable value to make constant name $chang = ' GEI '; echo $chang; ECHO constant (' GEI '), ' <br/> '; echo constant ($chang), ' <br/> '; echo "<br/>";

3. File Introduction

File contains: The role of code reuse, you can write the common code snippet to the file, when used to introduce the file//include ('./719.php '); $age = 1;function B () {echo ' Hello ';} <?php$age + = 1;? >include ('./719.php ');//equivalent to 719. PHP file Contents replace Bank/*include ('./7192.php ');//include ('./7192.php ');//include ('./7192.php '); */include_once ('./7192.php '); );//_once is only introduced once, does not duplicate references include_once ('./7192.php '); include_once ('./7192.php '); B (); Echo $age; Require_once ('./71922. php ');//Add _once speed slow//require and include the difference, include as far as possible to execute, reported Warning;require direct fatal, script immediately stop execution

4. In-depth explanation of the system

/* life commonly used in 10 binary computers commonly used 2 binary, 8, 16 binary *///10 echo 123;//a top, a top ten, a top hundred echo 3*1 + 10-2 + 100*1;//8, front with 0 for octal Echo 0123;//a top one, a top eight, A 64//16, the front plus 0x represents 16echo 0x123;//a top one, a Top 16. A top 256//2, PHP currently does not support direct representation//A top 1, a top 2, a top 4, a 8......//10 2-in//5 0000 0101//2 55 128+64+32+16+8+4+2+4 11111111//-1 11111111//8 1 in the end to understand the 255 or 1, depending on the program//such as in MySQL. The Internet understands that -1,unsigned Internet is understood to be 255//10 in binary notation 0 1 2 3 4 5 6 7 8 9 a B c D E F echo 0x1c;

This article from "A Big big waste fish" blog, declined reprint!

Abandoned fish--how long does PHP take to get from getting started to giving up? 12