Programming PHP

Query-string encoding
The urlencode( ) and urldecode( ) functions differ from their raw counterparts only
in that they encode spaces as plus signs (+) instead of as the sequence %20. This is the
format for building query strings and cookie values, but because these values are
automatically decoded when they are passed through a form or cookie, you don’t
need to use these functions to process the current page’s query string or cookies. The
functions are useful for generating query strings:
SQL
$base_url = 'http://www.google.com/q=';
$query = 'PHP sessions –cookies';
$url = $base_url . urlencode($query);
echo $url;
http://www.google.com/q=PHP+sessions+-cookies
Most database systems require that string literals in your SQL queries be escaped.
SQL’s encoding scheme is pretty simple—single quotes, double quotes, NUL-bytes,
and backslashes need to be preceded by a backslash. The addslashes( ) function
adds these slashes, and the stripslashes( ) function removes them:
$string =