Replace letter "A" if preceded by a digit

Question

This code str_replace('A', ' Amp', $var) can convert 2.7A to 2.7 Amp.

But, it should not convert A2 to Amp 2.

Can preg_replace() with a regex pattern solve this issue?

Answer 1

Use a positive lookbehind beased regex to match all the A's which exists just after to a digit.

(?<=\d)A

Then replace the matched A with Amp.

DEMO

echo preg_replace('~(?<=\d)A~', 'Amp', $str);