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Use of string type "PHP Basics"

2022-07-27 08:07:00 【Go home at night】

Functional requirements

Apply single quotation marks and double quotation marks to output the same variable , The output results are completely different , The double quotation marks output the value of the variable , The output of single quotation marks is a string .

The sample code 

<!doctype html>

<html>

<head>

<meta charset="utf-8">

<title> Use of single and double quotation marks </title>

</head>



<body>

<?php

  echo '\'\\<br />';  // Output ：'\

  $a = 10;

  echo 'The a value is $a <br />';

  echo "The a value is $a <br />";

?>

</body>

Running results

 

 

Knowledge description

A string is a sequence of consecutive characters , By digital 、 A combination of letters and symbols . Each character in the string takes only one byte . stay PHP in , Defining strings mainly uses single quotation marks （'） And double quotes （"） Two ways .

（1） Single quotation marks can be used to define strings “'” Cover up , If you want to represent single quotes in a string , Escape character is required “\” The single quotation mark can only be output after being converted . If a backslash appears before a single quotation mark or at the end of the string “\”, Use two backslashes to indicate .

Single quotation marks define the format ：

$a = ' character string ';

（2） Use double quotes “"” Enclosing a string can also define a string . If you want to represent double quotation marks in the defined string , You also need to use escape characters to transfer .

Double quotation marks define the format ：

$a = " character string ";

The difference between the two is , Variables contained in double quotes are automatically replaced with actual values , The variables contained in single quotation marks are output as ordinary strings .

When using escape characters , Use single quotes , Just use single quotation marks “'” Escape , But use double quotation marks “"” when , Also note the double quotation marks “"”、“$” The use of characters such as . These special characters must pass through the transfer character “\” To display . Commonly used escape characters .

 

 

\n and \r stay Windows There is no difference in the system , Can be used as a carriage return . But in Linux There are two effects in the system , stay Linux in \n Change to the next line , But will not return to the beginning of the line ; and \r Indicates that the cursor returns to the beginning of the line , But still in the bank .

Be careful ： If you use “\”, So when outputting ,“\” It will also be output together .

explain ： When defining a simple string , Using single quotation marks is a more appropriate treatment . If you use double quotes ,PHP It will take some time to deal with the escape of strings and the parsing of variables . therefore , When defining a string , If there are no special requirements , Try to use single quotation marks .

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