Need help with bash script using sed

I have been trying for hours to find and replace text in a file using sed for a script. I think the problem is a regex issue, but not sure.

I am trying to replace the line below in a php file while in a ssh jail.

Code:

define('DB_HOST', 'localhost');

Here's what I want to replace it with.

Code:

if ( defined( 'WP_CLI' ) && WP_CLI ) {
define('DB_HOST', '127.0.0.1:3306');
} else {
define('DB_HOST', 'localhost'); }

Someone told me it's easier to put the replacement code in a text file and add it using sed. Is that correct? If so, how?

Below is what I've tried. Note: I added .* in case :3306 at the end of localhost. Could be wrong, too, but I have tried it without .* as well.

Code:

sed -i 's/define\(\'DB\_HOST\'\,\ \'localhost.*\'\)\;/if\ \(\ defined\(\ \'WP\_CLI\' \)\ \&\&\ WP\_CLI\ \)\ \{/ndefine\(\'DB\_HOST\'\,\ \'127\.0\.0\.1\:3306\'\)\;/n\}\ else\ \{/ndefine\ \(\'DB\_HOST\'\,\ \'localhost\'\)\;\ \}' wp-config.php

When I run it from the command line (Debian Jessie), it displays >

Code:

[email protected]:/web$ sed -i 's/define\(\'DB\_HOST\'\,\ \'localhost.*\'\)\;/if\ \(\ defined\(\ \'WP\_CLI\' \)\ \&\&\ WP\_CLI\ \)\ \{/ndefine\(\'DB\_HOST\'\,\ \'127\.0\.0\.1\:3306\'\)\;/n\}\ else\ \{/ndefine\ \(\'DB\_HOST\'\,\ \'localhost\'\)\;\ \}' wp-config.php
>

What am I doing wrong? I've also tried with /r instead of /n, and added /g to the end.
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