PHP date_parse_from_format( ) alternative in PHP 5.2

Question

Since date_parse_from_format( ) is available only in PHP 5.3, I need to write a function that mimics its behaviour in PHP 5.2.

Is it possible to write this function

Answer 1

If you want it to be exactly like PHP 5.3 function, you're gonna need a lot of code. I'd start with something like this:

$format = '\Y: Y-m-d';
var_dump($format);

$date = date($format);
var_dump($date);

// reverse engineer date formats
$keys = array(
    'Y' => array('year', '\d{4}'),
    'm' => array('month', '\d{2}'),
    'd' => array('day', '\d{2}'),
    'j' => array('day', '\d{1,2}'),
    'n' => array('month', '\d{1,2}'),
    'M' => array('month', '[A-Z][a-z]{2}'),
    'F' => array('month', '[A-Z][a-z]{2,8}'),
    'D' => array('day', '[A-Z][a-z]{2}'),
    // etc etc etc
);

// convert format string to regex
$regex = '';
$chars = str_split($format);
foreach ( $chars AS $n => $char ) {
    $lastChar = isset($chars[$n-1]) ? $chars[$n-1] : '';
    $skipCurrent = '\\' == $lastChar;
    if ( !$skipCurrent && isset($keys[$char]) ) {
        $regex .= '(?P<'.$keys[$char][0].'>'.$keys[$char][1].')';
    }
    else if ( '\\' == $char ) {
        $regex .= $char;
    }
    else {
        $regex .= preg_quote($char);
    }
}

var_dump($regex);

// now try to match it
if ( preg_match('#^'.$regex.'$#', $date, $matches) ) {
    foreach ( $matches AS $k => $v ) if ( is_int($k) ) unset($matches[$k]);
    print_r($matches);
}
else {
    echo 'invalid date "'.$date.'" for format "'.$format.'"'."\n";
}

Result:

string(9) "\Y: Y-m-d"
string(13) "Y: 2011-07-12"
string(51) "\Y\: (?P\d{4})-(?P\d{2})-(?P\d{2})"
Array
(
    [year] => 2011
    [month] => 07
    [day] => 12
)

Incomplete and imperfect.