matching a simple 2 letters in a string

[raghujosh]

I have a string
$initial_string = ""

In this I want to match the letters 'cb' and replace it with '1cb'.
The final string should look like this
$final_string = ""

My code is as follows. But nothing works. I have tried all tricks. Help will be greatly appreciated.

if (preg_match("cb", $initial_string))
{
$pattern = "cb";
$pat = "1cb";
$replacement =  "$pat";
$final_string = preg_replace($pattern, $replacement, $initial_string);
echo "$final_string";
}

[digital-ether]

The $pattern must be a regular expression. It must have delimiters around the pattern, and optional modifiers after the second delimiter.

Example patterns:

"/cb/" - matches cb
"/cb/i" - matches upper and lower case cb

see the docs for preg_match. http://php.net/preg_match

[raghujosh]

The $pattern must be a regular expression. It must have delimiters around the pattern, and optional modifiers after the second delimiter.

Example patterns:

"/cb/" - matches cb "/cb/i" - matches upper and lower case cb

see the docs for preg_match. http://php.net/preg_match

Thanks.It worked like charm