Summary of the differences between the strstr, strrchr, substr, and stristr functions in PHP, strstrstristr_PHP tutorial

Summary of the differences between the strstr, strrchr, substr, and stristr functions in php, strstrstristr

The difference in usage of the four functions strstr, strrchr, substr, and stristr in php:

The four string operation functions strstr strrchr substr stristr in PHP are particularly confusing. The commonly used ones are substr and strstr, which can basically satisfy the operation of strings.

The following is an introduction to the differences between these functions.

1. The difference between strstr and strcchr

strstr displays the first string found, the string to be found, and subsequent strings.
strrchr displays the last string found, the string to be found, and the following strings.

The results are as follows:

strstr test results @test.com@jb51.net
strrchr test results @jb51.net

2. The difference between strstr and strstr

strstr is case sensitive.
stristr is case-insensitive.

The results are as follows:

strstr test results jb51.net
stristr test results Ying@jb51.net

3. The difference between strstr and substr

strsr is intercepted after matching.
substr does not match and is intercepted based on the starting position.

The results are as follows:
strstr test results jb51.net
substr test results jb51.net

After understanding these string interception functions, you can save a lot of trouble during development

$a = array();
$a[] = "Project";
$a[] = "Title";
$a[] = "Time";
return $a

In fact, there is no need to search everywhere for so-called "commonly used functions". The so-called "commonly used functions" vary from person to person. Someone often uses a certain function, but it does not mean that you will also use it frequently. There are many PHP functions. It is key to always have a PHP help manual. If you encounter something you are not familiar with, check it out. The more times you check it, the more often it will become "commonly used".

Generally speaking, string, array, and database class functions are relatively commonly used categories.

The functions are listed below for reference only.

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//================================Time and Date========= ======================
//y returns the last two digits of the year, the four-digit number of year Y, the number of month m, and the English month of M. d number of the month, D day of the week in English
$date=date("Y-m-d");

//include,include_once.require,require_once
//require("file.php" ) Before the PHP program is executed, the files specified by require will be read in. If an error occurs, it will be fatal.
//include("file.php") can be placed anywhere in the PHP program. The file specified by include will not be read until the PHP program is executed. If an error occurs,

//= ==============================Output printing================== =============
//sprintf("%d","3.2") ;//Only formatting, return the formatted string, no output.
//printf("%d","3.2") ;//Formatting and output
//print("3.2") ;//Only output
//echo "nihao" ,"aa";//Can output multiple strings
//print_r(array("a","b","c"));//Display the key values ​​and elements of the array in sequence

//============================== Commonly used string functions========== =====================

//Get the length of the string, how many characters there are, spaces are also counted
$str=" sdaf sd ";
$len=strlen($str);

//Use the string in the first parameter to connect each element in the subsequent array and return a string.
$str=implode("-",array("a","b","c"));

//String splitting method, returns an array, using the first parameter The characters in will split the following string, and intercept the characters before, after, and between the specified characters. If the specified character is at the beginning or end, the element at the beginning or end of the returned array will be an empty string
//If it is not divided into a string, Returns a null value to the corresponding element of the array. The last limit returns the length of the array. If there is no limit, it will continue to be divided.
$array=explode("a","asdd...the rest of the text>>