What is the purpose of strlen($query)-2;

Question

I got this code from google and it fulfills my requirement, but I don't understand the meaning of this line:

substr($query,0,strlen($query)-2)

Could somebody explain it to me?

<?php
function insert($tablename, $parameter_order, $values)
{
    $query = "insert into $tablename (";
    foreach($parameter_order as $po)
    {
        $query .= $po.', ';
    }
    $query = substr($query,0,strlen($query)-2).') values (';
foreach($values as $v)
{
$query .= "'$v', ";
}
$query = substr($query,0,strlen($query)-2).');';
    return $this->makeQuery($query);
}
?>

Do you understand what `substr` and `strlen` each do by themselves? It should then be obvious what they do when you put them together. — Barmar, Apr 25 '15 at 07:40
You should really not use this and switch to prepared statements instead. — jeroen, Apr 25 '15 at 07:40
@Barmar True, you would need a white-list as well. For the table name as too. Like I said, don't use this :-) — jeroen, Apr 25 '15 at 07:41
You should think about what you need. Do you really need a generic insert function like this? If so, you need to start over using the comments above to make it secure against sql injection. And you can post back here if you run into specific problems. — jeroen, Apr 25 '15 at 07:48
@ManiKandan: People will often downvote a question if they feel you haven't put much effort into a problem before asking here. You can prevent that by explaining in detail what you have tried or how you have understood the problem. Read more about [How to Ask a Good Question](http://stackoverflow.com/help/how-to-ask). — Michael Jaros, Apr 25 '15 at 07:51
Am honored with 4 down votes... Thanks. That's all i can say — Mani Kandan, Apr 25 '15 at 07:54
@jeroen: I no need your suggestion, just ans to the question else better you .... Understand it..!!! — Mani Kandan, Apr 25 '15 at 09:17

Michael Jaros · Answer 1 · 2015-04-25T07:47:41.973

1

The line removes the last comma and space from $query. These characters have been added in the foreach loop to glue together the elements of $parameter_order.

Note that this standard task is usually done better with the implode() function:

$query = "insert into $tablename (" . implode (', ', $parameter_order) . ' ) values (';

edited Apr 25 '15 at 07:47

answered Apr 25 '15 at 07:39

Michael Jaros

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Your confusing me.. Where will this line fit exactly in my code – Mani Kandan Apr 25 '15 at 07:50
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@ManiKandan: I wrote this line for you to learn, not to put it in your code. You usually use a statement like that instead of a `foreach` loop if you want to concatenate elements of an array. If you have no idea what I'm talking about, maybe you should start with some basic PHP tutorials. – Michael Jaros Apr 25 '15 at 07:55

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

This is what those functions do exactly:

substr() is used to generate a sub-string of specified length from another string.

strlen() will return the length of the provided string.

Code substr($query,0,strlen($query)-2) removes comma and space from foreach Loop.

edited Jun 20 '20 at 09:12

Community

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answered Apr 25 '15 at 07:44

Hardik Bharadava

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What is the purpose of strlen($query)-2;

2 Answers2