PHP variable name and SQL table column name length - php

Question

I have this really newbie question :)
Despite the the fact that
$lastInvoiceNumber
$lastInvNum
or:
last_invoice_number (int 10)
last_inv_num (int 10)
Save a bit of time to write. Do they have any benefits (even the slightest)
performance-wise?
Long vs short?
Is there any chance php and MySQL more importantly will consume
less memory if the query had a shorter table column name?
For example if I have to fetch 500 rows on a single query I imagine
the query would run 500 times and running
last_invoice_number 500 times
vs running
last_inv_num can save some memory or make things slightly faster.
Thanks.

Answer 1

No, there is really no noticeable difference in performance whatsoever, and you'll gain a huge improvement in readability by using descriptive variable names. Internally, these variables are referred to by memory addresses (to put it simply), not by their ASCII/Unicode names. The impact it may have on performance, in nearly any language, is so infinitesimal that it would never be noticed.
Edit:
I've added a benchmark. It shows that there is really no difference at all between using a single letter as a variable name and using a 17-character variable name. The single letter might even be a tiny bit slower. However, I do notice a slight consistent increase in time when using a 90-character variable name, but again, the difference is too small to ever notice for practical purposes. Here's the benchmark and output:
<?php
# To prevent any startup-costs from skewing results of the first test.
$start = microtime(true);
for ($i = 0; $i<1000; $i++)
{
$noop = null;
}
$end = microtime(true);
# Let's benchmark!
$start = microtime(true);
for ($i = 0; $i<1000000; $i++)
{
$thisIsAReallyLongAndReallyDescriptiveVariableNameInFactItIsJustWayTooLongHonestlyWtf = mt_rand(0, 1000);
}
$end = microtime(true);
printf("Using a long name took %f seconds.\n", ($end - $start));
$start = microtime(true);
for ($i = 0; $i<1000000; $i++)
{
$thisIsABitTooLong = mt_rand(0, 1000);
}
$end = microtime(true);
printf("Using a medium name took %f seconds.\n", ($end - $start));
$start = microtime(true);
for ($i = 0; $i<1000000; $i++)
{
$t = mt_rand(0, 1000);
}
$end = microtime(true);
printf("Using a short name took %f seconds.\n", ($end - $start));
Output:
$ php so-test.php
Using a long name took 0.148200 seconds.
Using a medium name took 0.142286 seconds.
Using a short name took 0.145952 seconds.
The same should be true for MySQL as well; I would almost guarantee it, but it's not as easy to benchmark. With MySQL, you will have far more overhead from the network and IO than anything to do with symbol naming in the code. Just as with PHP, internally, column names aren't just strings that are iterated over; data is stored in memory-efficient formats.