String manipulation problem

[denhamd2]

Hi,

 

I have a date stored in variable $date in the format 12032008

 

I'm looking to create a new variable $datereformatted in the format 20080312,, would anyone know how to do this in PHP?

[effigy]

<pre>
<?php
$str = '12032008';
echo preg_replace('/\A(\d{2})(\d{2})(\d{4})\z/', '$3$2$1', $str);
?>
</pre> 

[dave420]

<?php
$str = '12032008';
echo substr($str, 4, 4).substr($str, 2, 2).substr($str, 0, 2);
?>

 

Is significantly faster than using regular expressions.

[effigy]

Is significantly faster than using regular expressions.

 

One substr is, but what about multiple? And against an exact expression?

[dave420]

Well, it's not an exact expression - it still has to be matched against the string, bits of it captured, and then reconstituted in its final form.  I ran it through xdebug, and the preg_replace took up most of the time every single time I ran a test.  Regular expressions have quite an overhead compared to simply moving three bits of a string around using substr.

[effigy]

It's exact in the sense that there is no flexibility in the pattern; therefore, the engine doesn't juggle characters around trying to match: the first mismatch is an immediate failure.

 

Can you post some hard comparison numbers? I'm curious because I know that, yes, you wouldn't use a regexp to replace one character when you can use str_replace, but beyond that what do the numbers reflect?