How to convert textarea line breaks in php forms

It took a long time to debug the problem of converting the carriage return and line feed in the textarea to br and storing it in the database. That is, converting the line feed in the textarea.

1. You must know that the newline character in textarea is n (personal testing found that pressing the Enter key is n, it seems to be rn under Linux)

2. Before using nl2br, please read the manual explanation carefully. I am just frustrated. I generally understand it as converting n to
, which is not true:

See the php manual for explanation:

nl2br – Inserts HTML line breaks before all newlines in a string

Returns string with ‘
’ inserted before all newlines

means to insert before a new line

W3cschool says:

nl2br() function inserts an HTML newline character (
) before each new line (n) in a string.

So nl2br() can be inserted
but n still exists. For example, the string source code is: program n life network, after our nl2br is the program
n life network, so the effect we see will be

Program

Life.com——————-line break because there is n

3. Use PHP function, str_replace to replace the function, such as str_replace('n','
'). The problem is that the replacement is not successful and it has not been replaced. I have been doing it for a long time and even started to wonder whether the newline character in the textarea is n, thinking about it now is really shocking, o(∩_∩)o... In fact, after testing and replacing n /n respectively, I intuitively told me that I have entered a dead end. This is not a way to solve the problem. There must be something fundamental. mistake. Suddenly I thought about whether it was a problem with single quotes or double quotes, so I changed str_replace('n','
') to str_replace("n","
"), and the replacement was successful.

The explanation of single and double quotes in the manual is very detailed:

The easiest way to specify a simple string is to enclose it in single quotes (character ‘).

To represent a single quote, it needs to be escaped with a backslash (), like many other languages. If a backslash is required before a single quote or at the end of a string, use two backslashes. Note that if you try to escape any other characters, the backslash itself will also be displayed! So there's usually no need to escape the backslash itself.

If you enclose a string in double quotes ("), PHP knows more escape sequences for special characters:

Table 6-1. Escape characters

Sequence Meaning

n Line feed (LF or ASCII character 0×0A (10))

r Carriage return (CR or ASCII character 0×0D (13))

t Horizontal tab character (HT or ASCII character 0×09 (9))

\ Backslash

$ Dollar sign

” Double quotes

[0-7]{1,3} This regular expression sequence matches a character represented in octal notation

x[0-9A-Fa-f]{1,2} This regular expression sequence matches a character represented in hexadecimal notation

Also, if you try to escape any other characters, the backslash itself will be displayed!

The newline of textarea is not a problem of newline characters, nor is it a problem of nl2br. It is because all transfers only exist in double quotes. Single quotes only handle characters in PHP.

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