Pay attention to database security issues by accident as follows:

Accidentally pay attention to database security issues. The following table id field is the primary key auto-increment. if you want to delete a data entry, & quot; deletefromtestwhereid = & quot ;. $ _ POST ['id'] is it possible that this is not safe & quot; deletefrom accidentally pays attention to database security issues, as shown below
The id field of a table is the primary key auto-increment.

If you want to delete a data entry

So

"Delete from test where id =". $ _ POST ['id']

Is it possible that this is not safe?

"Delete from test where id =". $ _ POST ['id']

$ _ POST ['id'] = 2 or 1 = 1

Will this happen, resulting in deletion of all

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Yes, so quotation marks are generally added to the value type.
"Delete from test where id = '$ _ POST [id]'"
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Possible. This is often referred to as anti-SQL injection. Escape special characters.
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It is impossible to escape the characters after quotation marks.
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Intval
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Method 1: Set magic_quotes_gpc = Off in php. ini.

Method 2: $ str = stripcslashes ($ str)