Dynamic date definition and conditions

Question

I am building a small class combination to calculate the precise date of the beginning of a semester. The rules for determining the beginning of the semester goes as follow :

The monday of week number ## and after dd-mm-yyyy date

ie: for winter its week number 2 and it must be after the january 8th of that year

I am building a resource class that contain these data for all the semesters (4 in total). But now I am facing an issue based on the public holidays. Since some of those might be on a Monday, in those cases I need to get the date of the Tuesday.

The issue I am currently working on is the following :

The target semester begins on or after august 30 and must be on week 35. 

I also have to take account of a public holiday which happen on the first monday of september.

The condition in PHP terms is the following

if (date('m', myDate) == 9 // if the month is september
    && date('w', myDate) == 1 // if the day of the week is monday
    && date('d', myDate) < 7 // if we are in the first 7 days of september
)

What would be the best way to "word" this as a condition and store it in an array?

EDIT

I might not have been clear enough, finding the date is not the problem here. The actual problem is storing a condition in a configuration array that looks like the following :

$_ressources = array(
    1 => array(
        'dateMin' => '08-01-%',
        'weekNumber' => 2,
        'name' => 'Winter',
        'conditions' => array()
    ),
    2 => array(
        'dateMin' => '30-04-%',
        'weekNumber' => 18,
        'name' => 'Spring',
        'conditions' => array()
    ),
    3 => array(
        'dateMin' => '02-07-%',
        'weekNumber' => 27,
        'name' => 'Summer',
        'conditions' => array()
    ),
    4 => array(
        'dateMin' => '30-08-%',
        'weekNumber' => 35,
        'name' => 'Autumn',
        'conditions' => array("date('m', %date%) == 9  && date('w', %date%) == 1 && date('d', %date%) < 7")
    )
);

The issue I have with the way it's presented now, is that I will have to use the eval() function, which I would rather not to.

Answer 1

You said:

The target semester begins on or after august 30 and must be on week 35.

If that's the case you can simple check for week number.

if(date('W', myDate) == 35)

Or if your testing condition is correct then you should compare day number till 7 as it starts from 1.

if((date('m', myDate) == 9 // september
    && date('w', myDate) == 1 // monday
    && date('d', myDate) <= 7 // first 7 days of september
)

And then in the if statement, once you have found the monday which would be OK IF its not a public holiday, do this

if(...){
    while(!array_search (myDate, aray_of_public_holidays))
        date_add($myDate, date_interval_create_from_date_string('1 days'));
}

Here the array_of_public_holidays contains the list of public holidays.

Update with Code
Following code should work for your purposes

<?php
    // array with public holidays
    $public_holidays = array(/* public holidays */);

    // start on 30th august
    $myDate = new DateTime('August 30');

    // loop till week number does not cross 35
    while($myDate->format('W') <= 35){
        // if its a monday
        if($myDate->format('w') == 1){
            // find the next date not a public holiday
            while(array_search($myDate, $public_holidays))
                $myDate->add(date_interval_create_from_date_string('1 days'));

            // now myDate stores the valid semester start date so exit loop
            break;
        }
        // next date
        $myDate->add(date_interval_create_from_date_string('1 days'));
    }

    // now myDate is the semester start date
?>

Update according to updated question
Following code should work for your needs. You do not need to store the condition in your array as PHP code. The following code shows how it can be done

// semester conditions
$sem_conditions = array(
    1 => array(
        'dateMin' => '08-01-%',
        'weekNumber' => 2,
        'name' => 'Winter'
    ),
    2 => array(
        'dateMin' => '30-04-%',
        'weekNumber' => 18,
        'name' => 'Spring'
    ),
    3 => array(
        'dateMin' => '02-07-%',
        'weekNumber' => 27,
        'name' => 'Summer'
    ),
    4 => array(
        'dateMin' => '30-08-%',
        'weekNumber' => 35,
        'name' => 'Autumn'
    )
);

// array with public holidays format (d-M)
$public_holidays = array('05-09', '10-01');

// store sem starts
$sem_starts = array();

// for each semester
foreach($sem_conditions as $sem){
    // start date
    $myDate = date_create_from_format('d-m', substr($sem['dateMin'], 0, -2));

    // loop till week number does not cross $sem['weekNumber']
    while($myDate->format('W') <= $sem['weekNumber']){
        // if its a monday
        if($myDate->format('w') == 1){
            // find the next date not a public holiday
            while(array_search($myDate->format('d-m'), $public_holidays) !== false)
                $myDate->add(date_interval_create_from_date_string('1 days'));

            // now myDate stores the valid semester start date so exit loop
            break;
        }
        // next date
        $myDate->add(date_interval_create_from_date_string('1 days'));
    }

    // add to sem starts
    $sem_start[$sem['name']] = $myDate->format('d-m-Y');
}

var_dump($sem_start);

Answer 2

The target semester begins on or after august 30 and must be on week 35

The start of the semester is the minimal date between week 35 and August 30:

$week35 = new DateTime("January 1 + 35 weeks");
$august30 = new DateTime("August 30");

$start = min($week35, $august30);

Alternatively:

$start = min(date_create("January 1 + 52 weeks"), date_create("August 30"));