Just so you're aware, you can do something like

$string = str_replace(qr/(?:Hello)|(?:Hi)/, "Good-bye", "Hello My Name
+ is Elfyn");
[download]

qr creates something that allows you to embed regex operators within a string to be used in a regex. :-)

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.