PHP: analyse variable

Question

I am creating a website for school.

I have the subjects of a student saved in a database.

It's get saved like this --> 1,2,3,6,7

This means student X does subject ID 1,2,3, 6 and 7

The subjects from one student get returned from a database in one variable $subjects I would like to output the Subject Name (subject names are also stored in the database). But since the variable that is returned in $subjects is not one subject, but multiple, I can't search for the subject name. Is it possible to convert $subjects to an array so that $subjects[0] would be 1 in my example and $subjects[1] would be 2 (see above @ it's get saved like this).

Simply said: it should not be $subjects = 1,2,3,6,7 but

$subjects[0] = 1
$subjects[1] = 2
$subjects[2] = 3
$subjects[3] = 6
$subjects[4] = 7

You can get the database itself to give out the names directly, but for this to happen you must normalize the schema by creating a join table for the N-to-M relationship between students and subjects. Google a bit. — Jon
– Jon, Commented Aug 28, 2013 at 20:43

Paul · Accepted Answer · 2013-08-28 20:48:41Z

2

You can use explode to convert a string to an array:

explode(',', $students);

It should be noted, however, that exploding and then doing more queries to your database to get the subject names is a very inefficient way to do this. Rather that store students subjects in one field you should create a whole table for that relationship. So in additional to a Students table and a Subjects table, you have the relationship:

Table: StudentSubjects

Student | Subject
-----------------
   1    |   1
   1    |   2
   1    |   3
   1    |   6
   1    |   7
   2    |   2
   2    |   4
   2    |   6
   2    |   8
   3    |   3

Then you can query your database and get a list of subject names for a particular student, or group of students, in one query.

answered Aug 28, 2013 at 20:48

Paul

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Paul · Accepted Answer · 2013-08-28 20:51:01Z

0

You can choose 2 way:

explode :

<?php
$str = '1,2,3,6,7';
$chars = explode(',', $str);
print_r($chars);
?>

or preg_split:

<?php
$str = '1,2,3,6,7';
$chars = preg_split('/,/', $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($chars);
?>

edited Aug 28, 2013 at 20:51

Paul

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answered Aug 28, 2013 at 20:50

A1Gard

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1 Comment

Paul Over a year ago

There is no reason to use preg_split when explode will suffice.

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