Question

can regex recognize an sequence and perform actions based on it?

for example: I need regex to search for $string, then count BASED on x number of characters preceding $string and extract some data.

if anyone help me better word this question or suggest links it would be greatly appreciated!

Answer 1

you are looking for something called lookahead in regex.
For example the regex below will match only if there are 5 to 7 digits before the string
naturally – you will need to replace “string” with your own var.

if (eregi('[[:digit:]]{5,7}(?=string)', $subject)) {
    # Successful match
} else {
    # Match attempt failed
}