Detailed use of PHP magic_quotes_gpc_PHP tutorial

What we want to introduce to you today is 1.
Condition: PHP magic_quotes_gpc=off
The string written to the database has not been filtered in any way. The string read from the database is not processed in any way.

Data: $data="snow"''sun"; (There are four consecutive single quotes between snow and sun).

Operation: Change the string: "snow"' 'sun" is written to the database,

Result: SQL statement error occurs, mysql cannot successfully complete the SQL statement, and writing to the database fails.

Database saving format: No data.

Output data format: No data.

Note: Unprocessed single quotes will cause SQL statement errors when written to the database.

2.
Condition: PHP magic_quotes_gpc=off
The string written to the database is processed by the function addlashes(). The string read from the database is not processed in any way.

Data: $data="snow"''sun"; (There are four consecutive single quotes between snow and sun).

Operation: Change the string: "snow"' 'sun" is written to the database,

Result: The sql statement is executed smoothly and the data is successfully written to the database

Database saving format: snow"''sun (same as input)

Output data format: snow"''sun (same as input)

Explanation: The addslashes() function converts single quotes into ' escape characters so that the sql statement can be executed successfully,
but ' does not As data is stored in the database, the database saves snow''''sun and not the snow''''sun we imagined

3.
Conditions: PHP magic_quotes_gpc=on
Write to the database The string has not been processed in any way. The string read from the database has not been processed in any way: $data="snow"''sun"; (There are four consecutive characters between snow and sun. Single quote).

Operation: Write the string: "snow"''sun" into the database,

Result: The sql statement is executed smoothly, and the data is successfully written into the database

Database saving format: snow”''sun (same as input)

Output data format: snow”''sun (same as input)

Instructions: PHP magic_quotes_gpc=on will single quotes The escape character converted to ' causes the sql statement to be executed successfully,

but ' is not entered into the database as data. The database saves snow''''sun instead of snow''''sun as we imagined.

4.

Condition: PHP magic_quotes_gpc=on

The string written to the database is processed by the function addlashes(). The string read from the database is not processed in any way.

Data: $data="snow"''sun"; (There are four consecutive single quotes between snow and sun).

Operation: Change the string: "snow"' 'sun" is written to the database,

Result: The sql statement is executed smoothly and the data is successfully written to the database

Database saving format: snow''''sun (escape characters added)

Output data format: snow''''sun (with escape characters added)

Description: PHP magic_quotes_gpc=on converts single quotes into 'escape characters so that the sql statement can be executed successfully,

addslashes converts the single quotes that are about to be written into the database into ', and the latter conversion is written into the

database as data. The database saves snow''''sun

which is summarized as follows:

1. For PHP magic_quotes_gpc=on,

we can not perform

addslashes() and stripslashes() operations on the string data input and output from the database, and the data will be displayed normally.

If you perform addslashes() on the input data at this time,

then you must use stripslashes() to remove excess backslashes when outputting.

2. For the case of PHP magic_quotes_gpc=off

must use addslashes() to process the input data, but there is no need to use stripslashes() to format the output

because addslashes() The backslash is not written to the database together, it just helps mysql complete the execution of the sql statement.

Supplement:

PHP magic_quotes_gpc scope is: WEB client server; action time: when the request starts, such as when the script is running.

magic_quotes_runtime scope: data read from a file or the result of executing exec() or obtained from a SQL query; action time: every time the script accesses the data generated in the running state

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