I have a test file I use to test escaping of 'special' characters: 
\ = backslash
\\ = two backslashes
\\\ = three backslashes
' = a single quote
'' = two single quotes
\' = a backslash and a single quote
" = a double quote
\" = a backslash and a double quote
'"' = a double quote within 2 single quotes

Here's a test of formatting and odd characters. 
This is the second line. 

Blank line above and some characters below:

< = less than
> = greater than
& = ampersand
&amp; = an ampersand, a-m-p and a semicolon
! = exclamation

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Let's say I stick that into a variable $var and want to stuff it into a MySQL database table. To escape out these special characters, I run the variable through the DBI's quote() method: 
$var = $dbh->quote( $var ); # I could also use placeholders

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The problem, if it is one, is that when I look into the database, the single quotes are are properly escaped (ie. \') but the backslashes are not escaped (ie. a single backslash is represented by a single \ in the database).

Reading the DBI (and MySQL) docs, this doesn't seems to be the correct behaviour, since backslashes are supposed to be escaped with another backslash (ie. \\). So far I haven't gotten any errors and everything seems to be producing the expected results. But I'm wondering why this is. Is this correct behaviour? Shouldn't $dbh->quote() put an extra backslash in front of each backslash, or am I mistaken?

Also, please let me know if this is actually a MySQL question. I'm asking here because I'm using DBI's quote() function and I suspect that may be the culprit, for better or worse.

tia

In reply to Backslashes with DBI quote( ) and MySQL by doran

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