Question

I have a text file of HTML that includes the following marker set for replacement:
$$ausposttrackingid$$

I’m trying to replace that text using the following regex:

$trackingId="M6023409823490234";
$text = preg_replace("/\$\$ausposttrackingid\$\$/",$trackingId,$text);

But…it doesn’t replace the text at all, leaving the $$ausposttrackingid$$ alone.
I thought I’d escaped the $ signs properly, but no give.

Can anyone tell me how I should specify the regex in preg_replace to correctly pick up the $$ausposttrackingid$$? Or, alternately, should I use another tag marker instead of $ given its meaning in regexes?

Thanks guys.
Pete

Answer 1

Don’t use double quotes, because PHP will look for variable names inside your string and replace them for their value. So $ausposttrackingid in the string gets replaced with the value of the variable $ausposttrackingid. If that isn’t your intention, use single quotes:

$text = preg_replace('/\$\$ausposttrackingid\$\$/',$trackingId,$text);

In fact, get used to use single quotes, unless needed.

A working example:

<?php
    $text = 'Something $$ausposttrackingid$$ something else';
    $trackingId = 'M6023409823490234';
    $text = preg_replace('/\$\$ausposttrackingid\$\$/', $trackingId, $text);
    print_r($text);
    //The output is: Something M6023409823490234 something else
?>

---

Addendum

You will want to use double quotes for some scape characters, for instance "\n" will give you a new line but '\n' will not, instead it will just print \n.