SED find / replace code in php script - sed

Question

I have a large php script that contains the following line
$user = $_REQUEST['user'];
The exact match only appears once in the entire page. I want to change it to
$user = urldecode($_REQUEST['user']);
Can someone advise the best way ?
I'm thinking SED, but everything I've tried has failed to find and replace it.
Any ideas ?
Thanks

Answer 1

Following should help you in same.
sed 's/^$user = $_REQUEST\['"'"'user'"'"'\]\;$/$user = urldecode($_REQUEST\['"'"'user'"'"'\]);/' Input_file
Let's say following is the Input_file(I am assuming here).
cat Input_file
^#^#^#^#00000305^#^#^#^#^#^#430^#430^#^#^#^#^#^#^#^#^#09079989530
$user = $_REQUEST['user'];
tefqfwqfb$user = $_REQUEST['user'];
wvwrjvnwvjn$user = $_REQUEST['user'];fwvwrev
So after running above code following will be the output.
sed 's/^$user = $_REQUEST\['"'"'user'"'"'\]\;$/$user = urldecode($_REQUEST\['"'"'user'"'"'\]);/' Input_file
^#^#^#^#00000305^#^#^#^#^#^#430^#430^#^#^#^#^#^#^#^#^#09079989530
$user = urldecode($_REQUEST['user']);
tefqfwqfb$user = $_REQUEST['user'];
wvwrjvnwvjn$user = $_REQUEST['user'];fwvwrev

Answer 2

sed approach:
sed -E "s/^(\\\$user = )(\\\$_REQUEST\['user'\])/\1urldecode(\2)/" file.php

Answer 3

$ awk 'index($0,"$user = $_REQUEST[\047user\047];") { sub(/= /,"&urldecode("); sub(/;/,")&") } 1' file
$user = urldecode($_REQUEST['user']);

Answer 4

This might work for you (GNU sed):
sed '/^$user = $_REQUEST\['\''user'\''\];$/s/$_[^;]*/urldecode(&)/' file
Match the string and then use substitution to amend part of it.
N.B. '\'' closes the current single quoted sed command, introduces another single quote and then begins the rest of the sed command i.e. it punches a hole through to the shell and then quotes a single quote.