Pay attention to the use of escape characters\,",$
Pay attention to the use of octal or hexadecimal characters to represent xf6
echo "Hxf6me";//You need to check whether this type of text encoding is supported
--------- ------------Output results------------------------------------ ----
H鑇e
----------------------------------------- ----------------------------
1. Use printf() and sprintf() to create formatted output
printf() direct output To the output buffer
The output of sprintf() is returned as a string
For example, printf("Output content%.2fn",$PI());
All conversion specifications start with %
Data types include d-integer, s -String, f-floating point number, b-binary
.2 is an optional width indicator, and the output to the right of the decimal point is padded with 0
printf("%.2f",3.14159);
printf("%10.2f", 3.14159);
printf("%.10f",3.14159);
printf("%.9s",abcdefghijklmn);
printf("%5.2f,%f,%7.3fm",3.14159,3.14159,3.14159);
printf("%b %d %f %s n",123,123,123,"test");
------------------------Output results----- ----------------------------------
3.14 3.143.1415900000abcdefghi 3.14,3.141590, 3.142m1111011 123 123.000000 test
-------------------------------------------------- ------------------
2. String padding
string str_pad(string input original string, int length the total length after adding [, string padding characters to be filled [, int pad_type] padding type])
The padding type is added to the left STR_PAD_LEFT, the default is added to the right, and padding is added to both ends STR_PAD_BOTH
$index = array("one"=>1,"two"=>155, "three"=>1679);
echo "
";
echo str_pad("This is the title",50," ",STR_PAD_BOTH)."n";
foreach($index as $inkey=>$inval )
echo str_pad($inkey,30,".").str_pad($inval,20,".",STR_PAD_LEFT)."n";
echo "
";
--------- ----------Output results---------------------------------------- ---
This is the title
one...................................... .....1
two........................................ ..155
three........................................1679
-- -------------------------------------------------- ------------------
string strtolower(string subject)//Convert to lowercase
string strtoupper(string subject)//Convert to uppercase
string ucfirst(string subject)// Capitalize the first letter of each word
string ucwords(string subject)//Capital the first letter of each word
string ltrim(string subject)//Remove the left blank
string rtrim(string subject)//Remove the right blank
string trim(string subject) Left and right whitespace, whitespace includes null, tab character, newline character, carriage return character and space
string n12br(string source)//Convert the newline character represented by n to
mark
3. String comparison
integer strcmp(sting str1 , string str2) //str1 is greater than str2 and returns -1. str1 is less than str2 and returns 1. If str1 and str2 are equal, return 0.
integer strmcmp(sting str1, string str2, integer length) //The third parameter limits the comparison of length characters.
print strcmp("aardvark","aardwolf");
print strncmp("aardvark","aardwolf",4);
---------------------Output results ----------------------------------------
-10
------ -------------------------------------------------- -------------
strcasecmp() and strncasecmp() are case-insensitive comparison functions
4. Find and extract substrings
string substr(sting source,integer start[,integer length])//Take length characters from start
start and length can use negative values
$var = "abcdefgh";
print substr($var,2);//Start counting from 0
print substr($var ,2,3);
print substr($var,-1);//Start from the end of the string
print substr($var,-5,2);
print substr($var,-5,-2 );
---------------------Output result------------------------ ----------------
cdefgh
cde
h
de
def
----------------------- -----------------------------------------------
integer strpos( string haystack,string needle[,integer offset])//Find the position of the substring and return the first occurrence.
integer strrpos(string haystack,string needle)//Only search for a single character (only take the first for multiple characters ), returns the index of the last occurrence.
There are also common functions for extracting the found part from a string
string strstr(string haystack,string needle)//It is not case sensitive
string stristr(string haystack,string needle) )//Case sensitive
string strrchr(string haystack,sting needle)
**************** array explode(string separator,string subject[,integer limit])//Return a string array
array implode(string glue,array pieces)//Return a string
////////////////////////////Code segment///// /////////////////////////////////////
$guest = "this is a string";
$guestArray = explode(" ",$guest);
var_dump($guestArray);
sort($guestArray);
echo implode(",",$guestArray);
/////////////// ///////////////////////////////////////////////////// ////////
------------------------Output results------------------ -----------------------
array(4) { [0]=> string(4) "this" [1]=> string(2 ) "is" [2]=> string(1) "a" [3]=> string(6) "string" }a,is,string,this
------------------------------------------------ -----------------------------
5. Replace characters and substrings
string substr_replace(string source,string replace,int start[,int length])
The above introduces the common sense of mySQL traversing strings and PHP strings, including the content of mySQL traversing strings. I hope it will be helpful to friends who are interested in PHP tutorials.

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.

In PHP, use the clone keyword to create a copy of the object and customize the cloning behavior through the \_\_clone magic method. 1. Use the clone keyword to make a shallow copy, cloning the object's properties but not the object's properties. 2. The \_\_clone method can deeply copy nested objects to avoid shallow copying problems. 3. Pay attention to avoid circular references and performance problems in cloning, and optimize cloning operations to improve efficiency.

PHP is suitable for web development and content management systems, and Python is suitable for data science, machine learning and automation scripts. 1.PHP performs well in building fast and scalable websites and applications and is commonly used in CMS such as WordPress. 2. Python has performed outstandingly in the fields of data science and machine learning, with rich libraries such as NumPy and TensorFlow.

Key players in HTTP cache headers include Cache-Control, ETag, and Last-Modified. 1.Cache-Control is used to control caching policies. Example: Cache-Control:max-age=3600,public. 2. ETag verifies resource changes through unique identifiers, example: ETag: "686897696a7c876b7e". 3.Last-Modified indicates the resource's last modification time, example: Last-Modified:Wed,21Oct201507:28:00GMT.

In PHP, password_hash and password_verify functions should be used to implement secure password hashing, and MD5 or SHA1 should not be used. 1) password_hash generates a hash containing salt values to enhance security. 2) Password_verify verify password and ensure security by comparing hash values. 3) MD5 and SHA1 are vulnerable and lack salt values, and are not suitable for modern password security.

PHP is a server-side scripting language used for dynamic web development and server-side applications. 1.PHP is an interpreted language that does not require compilation and is suitable for rapid development. 2. PHP code is embedded in HTML, making it easy to develop web pages. 3. PHP processes server-side logic, generates HTML output, and supports user interaction and data processing. 4. PHP can interact with the database, process form submission, and execute server-side tasks.

PHP has shaped the network over the past few decades and will continue to play an important role in web development. 1) PHP originated in 1994 and has become the first choice for developers due to its ease of use and seamless integration with MySQL. 2) Its core functions include generating dynamic content and integrating with the database, allowing the website to be updated in real time and displayed in personalized manner. 3) The wide application and ecosystem of PHP have driven its long-term impact, but it also faces version updates and security challenges. 4) Performance improvements in recent years, such as the release of PHP7, enable it to compete with modern languages. 5) In the future, PHP needs to deal with new challenges such as containerization and microservices, but its flexibility and active community make it adaptable.

The core benefits of PHP include ease of learning, strong web development support, rich libraries and frameworks, high performance and scalability, cross-platform compatibility, and cost-effectiveness. 1) Easy to learn and use, suitable for beginners; 2) Good integration with web servers and supports multiple databases; 3) Have powerful frameworks such as Laravel; 4) High performance can be achieved through optimization; 5) Support multiple operating systems; 6) Open source to reduce development costs.


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