PHP: preg replace date time

Question

how can i replace date/time in this format 'Fri Mar 23 15:21:08 2012' with preg_replace? Date in this format is present couple of times in my text and i need to replace it with current time/date. Thanks, Chris

Accepted Answer

Well, what you need is an expression that will match 3 letters (`Fri`) followed by a space and another three letters (`Mar`).

First we need to match some letters:

```
/[a-z]/
```

We can match exactly 3 letters like this:

```
/[a-z]{3}/
```

...and we'll need it to be case insensitive:

```
/[a-z]{3}/i
```

...so the first part is just:

```
/[a-z]{3} [a-z]{3}/i
```

Next, we need to match either 1 or 2 numerics. A numeric can be represented with the escape sequence `\d`, so we'd use:

```
/\d{1,2}/
```

Next we match the time string, using the same escape sequence:

```
/\d{2}:\d{2}:\d{2}/
```

...followed by a final 4 digit year:

```
/\d{4}/
```

Put it all together and we get:

```
/[a-z]{3} [a-z]{3} \d{1,2} \d{2}:\d{2}:\d{2} \d{4}/i
// Fri       Mar      23     15 :  21 :  08    2012
```

Now, we need to replace it with the current date and time. The usual place we'd go for that is the `date()` function, but how to we get that into the replacement dynamically? Well we could pass it as a string literal, or we could use a callback function to get it from `preg_replace_callback()`. But, `preg_replace()` gives us the `e` modifier which causes the replacement string to be evaluated for PHP code. We have to be careful and sparing with it's use, as with any PHP `eval()`, but this is a legitimate use case.

So our final PHP code looks like this:

```
preg_replace(
  '/[a-z]{3} [a-z]{3} \d{1,2} \d{2}:\d{2}:\d{2} \d{4}/ie',
  "date('D M j H:i:s Y')",
  $str
);
```

See it working

PHP: preg replace date time

Solution

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