Fundamental Symbols and usage in PHP

In PHP, the basic symbols and core tips for using the method are as follows: after so long, the basic symbols of PHP have not been fully recognized. after seeing the @ number, I still found the question for half a day. post the basic symbol list. For more information, see. After using it for so long, the basic symbols of PHP were not fully recognized. I found the @ number and found out what it meant for a long time. I posted a basic symbol list in PHP and how to use it.

Core tips: after using it for so long, the basic symbols of PHP have not been fully recognized. I can see that the @ code has been found for a long time and I can see what it means. post the basic symbol list. For more information, see.

After using it for so long, the basic symbols of PHP were not fully recognized. I found the @ number and found it for a long time. post the basic symbol list. For more information, see ~

Annotation symbol:

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// Single line annotation /**/Multi-line annotation

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Use of quotation marks

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''Single quotes, no meaning, can be taken without any processing; "" Double quotes, php dynamic processing and output, usually used for variables.

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Variable form:

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True is True; The other is False.

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Common variables:

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String (numbers, Chinese characters, etc) Integer (1, 2, 3, 4, 5, 0,-1,-2, and so on) Double floating point number (decimal point) Array Object

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Available methods include gettype ($ mix) and settype ($ mix, $ typename );

Common symbols

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\ "Double quotation marks \ Backslash \ N line feed \ R output \ T hop (TAB)

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Operator Number

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+ Addition operation-subtraction operation * Multiplication/Division % Get remainder + + accumulate -- Accumulate 1. add strings

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Set operation

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= Place the value on the right to the left (Yes) + = Add the right value to the left -= Reduce the value on the right to the left * = Multiply the value on the left by the value on the right. /= Divide the value on the left by the value on the right . = Add the string on the right to the left

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Bitwise operator

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& | Or ^ Exclusive (xor) <Shift left > Shift to the right ~ 1 Population

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Logical operation

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<Less> greater <= Less than or equal to> = greater than or equal ! = Not equal to & and | Or! No

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Other operators

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$ Variable symbol & Variable indicators (before the variable) @ Do not display the error message (before the function) -> Object methods or attributes => Array element value ? : Ternary operator

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Basic method

1. PHP converts strings to uppercase and lowercase!

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Strtolower (); converts characters to lowercase letters Strtoupper (); converts uppercase letters

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2. PHP encrypted string (case sensitive)

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Md5 (); encryption Sha1 (); encryption

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3. quotation marks

I. single quotes are output as is

2. double quotation marks are output based on content interpretation

3. a single quotation mark is used to execute a command, such as 'pwd '.

4. "\" acts on translated characters. for example, "\ n" is a line break!

4. function: htmlspecialchars ()

This function converts special characters into HTML strings (&....;). The most common use case may be the message board for handling customer messages.

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& (And) & "(Double quotation marks)" <(Less than) to < > (Greater than) to>

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This function only converts the preceding special characters and does not convert all of them into the ASCII conversion defined in HTML.

5. batch output HTML content!

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Echo <EOT HTML output content... // Comments are output here! EOT; Print < HTML output content... // Comments are output here! EOT;

(Note: "{variable}" is used for internal variables }")

6. determine whether the file exists and the output content

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$ FileName = "File. TXT "; If (File_Exists ($ FileName )){ Echo" ". File_Get_Contents ($ FileName )." "; } Else { Echo "no "; } ?>

7. unset the variable;

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Unset ($ var ); Unset ($ var, $ var1 );

8. is_int;

Checks whether the variable is an integer;

9. is_null;

Checks whether the variable is NULL;

10. is_string

Checks whether the variable is a string.

11. is_real;

Is_float () alias

12. isset

Check whether the variable is set

13. is_bool

Check whether the variable is Boolean

14. is_array

Checks whether the variable is an array.

15. is_object

Checks whether a variable is an object.

16. SubStr.

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SUBSTR (String, Start, SelectNum) Echo substr ('abcdef', 1); // bcdef Echo substr ('abcdef', 1, 3); // bcd Echo substr ('abcdef', 0, 4); // abcd Echo substr ('abcdef', 0, 8); // abcdef Echo substr ('abcdef',-1, 1); // f

17. Nb2br

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Echo nl2br ("foo ISN'T \ n bar ");

Convert the escape line into HTML