php strtotime() function returns blank/0

I have datetime data in string format like this:

Sat Mar 24 23:59:59 GMT 2012

I want to convert this into a UTC timestamp, but when I try it as follows:

function texttotime($texttime)
{
    if(!$texttime || $texttime=="")
        return NULL;

    // Sat Mar 24 23:59:59 GMT 2012
    $bits = preg_split('/\s/', $texttime);

    //                  Mar     24      2012    23:59:59    GMT
    return strtotime("$bits[1] $bits[2] $bits[5] $bits[3] bits[4]");
}

It outputs 0 (not NULL).

If I change the last line to:

    //                  Mar开发者_如何学编程     24      2012    23:59:59
    return strtotime("$bits[1] $bits[2] $bits[5] $bits[3]");

It outputs something (but the wrong timestamp, off by -4 hours or so).

Not quite sure why you're re-organising the existing string, as...

echo $timestamp = strtotime('Sat Mar 24 23:59:59 GMT 2012'); 

...works correctly. (It returns 1332633599, which you can check via date('r', 1332633599); (This will result in "Sat, 24 Mar 2012 23:59:59 +0000", so all is well.)

That said, if you're going to extract all of the components of the string, you might as well use mktime. For example:

function texttotime($texttime) {
    if(!$texttime || $texttime=="") return NULL;

    list($junk, $month, $day, $time, $timezone, $year) = explode(' ', $texttime);
    list($hour, $minute, $second) = explode(':', $time);

    return mktime($hour, $minute, $second, $month, $day, $year);
}

The reason you have 4 hour difference is caused by server timezone which is -4 hours from GMT. try to define your current timezone like this:

date_default_timezone_set('Europe/London');

$result = strtotime('Sat Mar 24 23:59:59 GMT 2012');

echo date('r', $result);//Sat, 24 Mar 2012 23:59:59 +0000