variable substitution

Hello again; I have two variables declared in the global scope of a script. $string_a = 'stuff $string_b and more stuff'; $string_b = ''; One is a string with a reference for substitution to the other string which is empty. In the processing body of the script are if/if else blocks. In these blocks I want to use $string_a and set $string_b to a value if( condition) { $string_b = 'by the way;';... etc so $string_a should read: "stuff and by the way; and more stuff" But this substitution will not take place in the context of the else if block. I do not want to write $string_a in at least 5 different if else blocks because it is about 10 lines intended to be an e-mail message body -> !SPAM. this script is used to process data sent from a link in another e-mail message used to validate and e-mail address. Q: Is there a way to get the substitution to take

    place here? (by reference, maybe?)

Thank you in advance for info Jeff K