PHP basic tutorial PHP built-in function example tutorial_PHP tutorial

So Aiwei.com will now explain the PHP built-in functions
There are functions related to case conversion
Text html tag processing functions

Case-related functions

Copy Code The code is as follows:

strtolower()
strtoupper()
ucfirst()
ucword()

String formatting functions related to HTML tags

Copy code The code is as follows:

nl2br()
htmllentities ()
htmlspecialchars()
stripslashes()
strip_tags()
number_format()
strrev()
md5()

All string processing functions in php do not modify the original string, but return a newly formatted string

Copy code The code is as follows :

//Convert to lowercase
$a='www.jb51.net';
echo strtolower($a);
//Result: www .jb51.net

//Convert to uppercase
$a='www.jb51.net';
echo strtoupper($a);
//Result: WWW.jb51. net

//Capitalize the first letter
$a='www.jb51.net';
echo ucfirst($a);
//Result: Www.jb51.net

//The first letter of each word is capitalized
$a='i love you';
echo ucword($a);
//Result: I Love You

/*
Tip: Everyone knows about capitalization. Do you think there is a difference between lowercase and uppercase? But why should we distinguish between uppercase and lowercase?
In PHP, case is not strict under the win system, but it is strictly prohibited under the linux system. You cannot write random
such as
when automatically loading a class
function _autoload($className){
include strtolower($className).'.class.php';
}
$obj= new MyClass;
This will load myclass.class.php
Because the file name is often lowercase, it must be converted to lowercase
?>
*/

//nl2brConvert spaces into entities
Because usually the line breaks displayed in the browser are
For example, in the form guestbook, it must be converted, otherwise the line breaks will not be successful. Multiple spaces are assigned a space
$a='
i
love
you
';
echo $a;
echo nl2br($a);
Result 1: i love you
Result 2:
i
love
you

//Form submission, if you do not process html tags, the style will be displayed directly or js code runs directly
/*

When you enter

www.jb51.net

As soon as you submit, the number one will appear Font
But you originally wanted the

www.jb51.net

result
, so you have to deal with it
when entering <script>alert('www.jb51. net')</script>
Javascript will be run as soon as it is submitted
This is not good and must be dealt with to prevent hackers from finding the entrance to your attack
The default submission method of the form is get
*/
//When you enter

www.jb51.net

echo htmlspecialchars($_GET['title']);//Filtered
results :

www.jb51.net

🎜>Another important point is that if you don’t deal with

some copied articles have tag styles themselves, which will disrupt your page layout and may cause css conflicts
The usage of htmllentities() function is opposite to that of htmlspecialchars() Not to mention

When you need to keep that tag, you can use the strip_tags() function
echo strip_tags($_GET['title'],'

');
The submission result is that if you check the source code, you will find that

is gone

/*
Add the input i love 'jb51';
The submission result is i love 'jb51' The backslash is escaped
So what should I do if I want to output the original text?
I can use this php function stripslashes()
Unescaping
echo stripslashes($_GET[' title']);
The result is i love 'jb51';
What if it contains an html tag like this
i love 'jb51'
What should I do if I want prototype output? I can combine two functions and use what I have already said
echo htmlspecialchars(stripslashes($_GET['title']));
Result: i love 'jb51'
*/

//number_format()this The function is a formatted currency function. Different countries have different habits, so the required currency display is different. For example, Chinese money in the mall is usually formatted like this
Use commas to separate thousands of places and keep the number of digits. Use the dot to pronounce 'decimal point'
The usage of this function is very simple
number_format($money, how many decimal points should be retained, 'how to separate decimal points', 'how to separate thousandths')
$price='123465789.233';
echo number_format($money,2,',','.');
Result: 123.465.789, 23
echo number_format($money,2,'.',',');//Chinese style The
result: 123,465,789.23

//strrev() reverses the string
$str='http://www.jb51.net';
echo strrev($str) ;
Result: moc.tenwii.www//:ptth

//md5 is the encrypted username and password and must be encrypted to prevent hackers
$a='admin';
echo $b = md5($a);

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www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/325714.htmlTechArticleSo Aiwei.com will now explain that php built-in functions have case conversion related functions. Text html tag processing functions are related to case. The function copy code is as follows: strtolower() strtoupper()...