John Davidson

Message:

I have the following code:

$f = 'IMG_1474.PNG';

preg_replace('/(.*)([.][^.]+$)/', '$1' . time() . '$2', $f)

which should split the IMG_1474 and .PNG and add the epoch in between. The first capture group appears to be empty though.

If preg_match is used I can see the first capture group is not empty (so regex performs the same in PHP as on regex101).

preg_match('/(.*)([.][^.]+$)/', $f, $match);

print_r($match);

Functional demo: https://3v4l.org/VgDWJ (the 604147502 is the time() result)

My presumption is that something is happening with the concatenation on the replace bit.

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My Answer:
To capture the first group in the replacement string in `preg_replace`, you can use `${1}` instead of `$1`. This will ensure that the captured group is properly replaced in the output. Here's the updated code:

php
$f = 'IMG_1474.PNG';
echo preg_replace('/(.*)([.][^.]+$)/', '${1}' . time() . '${2}', $f);


This will output something like `IMG_14741604147502.PNG`, where `1604147502` is the epoch time inserted between `IMG_1474` and `.PNG`.