PHP Foreach循环查询

Question

I've been tinkering with PHP lately (self-taught, no formal training), trying to understand how to grab data from a database and display the data somewhere. So far I have learned quite a bit, but now I am stumped.

I have a list of about 200 users in my local database in a table called site_members. The table has three fields: id, name, birth_date. Via PHP, I want to display all the users on a webpage, and have something like "Birthday soon!" be mentioned right after their name. Something like this:

John Smith (Birthday soon!)

I haven't written the code to do this, because I usually write pseudocode first before actually diving into the coding part. Here's the pseudocode:

• Get the current date and time and convert it to Unix timestamp
• Start foreach loop and go through list of users
  
  • Query the database table, get the birthdate of a user by their id, and store it in a variable named bdate.
  • Convert bdate to Unix timestamp
  • Subtract the current date from bdate, convert it into days remaining, and store it in a variable called remaining_days.
  • If the user's bdate is within 15 days (remaining_days is less than 15)
    • Display their name, followed by (Birthday soon!)
  • otherwise
    • Just display their name only
  • End if
• End foreach loop

Here's my problem: With the above pseudocode once translated into actual code, there would be a database query made every time in that foreach loop. Some of the tutorials I consulted mentioned I should avoid that for efficiency reasons, and it makes sense. I ran Google searches to find something similar, but that didn't do much. I do not want anyone to write any actual code for me. I just want a better solution to the querying.

Thanks in advance!

Answer 1

I think your concept for the pseudo code is right, and you're understanding of doing multiple database queries is also right, you just tangled the two into giving you a wrong idea.

If you construct your select statement properly (that's basically what you'd be using to access the database), you actually pull the information for everyone out of the database and store it once in an array (or some other form of object). You can then start your foreach loop using the array as your value and perform the rest of your checks that way.

$date = date("m.d.y");
$people = ** insert your commands to grab the info from the DB **
foreach($people as $person) {
    // do your comparison checks and echo's etc in here
}

Does this make sense?

Answer 2

There can be two solutions to your problem:-

1:

Instead of making query for every user, first get the data for all the users.
Traverse the data using foreach loop php
Do the processing and display the results.

2:

Store the user date_of_birth in proper mysql date datatype
Change your mysql query to use date function to get all the users who match your date difference criteria and just display those users.

Answer 3

It seems you failed to read up properly on the relationship between SQL and PHP. If you actually posted code, then you could have been easily unstumped because there are many ways to do the simple task from legacy tutorials to current PDO or even MVC within in 5mins or less.

I'm not going to write the code but you need to change HOW you think in your "pseudo code".

The problem with your pseudo code is because you believe that the DB is not smart and you are doing it as if it was only for storage.

The correct pattern for PHP is the following:

1) use the Date function to retrieve current day + 15. Get month and day only.

2) you make a SQL query that retrieve all users who's birth_date field's month and day are GREATER THAN (or equal) to TODAY and who are less than or equal to today + 15 (day and month only)

3) execute the query.

4) with the returned data set (if any) you can choose two path depending situation and design

a) you can loop it with a simple FETCH which fetch each row retrieve and display name and extra message.

or

b) iterates through the result set and store the display message into a variable and then finally display it once the iteration is done.

(option b is prefered because its more flexible since you can use this technique to out into a file instead of an echo)

THIS pseudo-code ensures that you are only retrieve the correct data set with the aid of the SQL system (or storage system).

Answer 4

In terms of overall process, aashnisshah is absolutely correct. First, you should retrieve all the records you need from your database then loop through each row to do your data comparisons and finally close the loop.

As for finding out if their birthday is close and if you want MySQL to do the hard work, you can build your query like that in PHP:

$query = "SELECT *, DATEDIFF(DATE_FORMAT(dob, '" . date('Y') . "-%m-%d'), CURDATE()) AS days_to_dob FROM Members";

The idea is to fetch an extra column called 'days_to_dob' containing the amount of days until that person's date of birth. Note that it will be negative if that date has passed for this year. With that extra column you can easily evaluate whether their dob is within 15 days.

Answer 5

If you don't want any php code, then here is my pseudocode:

Get date  and time -> UTC stamp and store in $time_current
Get all from site_members and store in $data
for each entry in $data, store in $record
    get birth_date from $record and convert to utc stamp and store in $birthday
    print name from $record
    if $birthday is close to $time_current then print "Birthday soon" end if
    print new line
end for

That performs only one request to your database.