The fixed cost of installing a PHP framework: disk size tells you nothing

The load measurement says how many requests a second each framework serves. This record chases a quieter question: what does installing that framework cost you when nothing is happening? How much disk does it occupy, how many files does it open per request, and what does the first visitor after a deploy pay?

The practical version of the question is: which of these numbers can you look at to decide that a framework is “heavy”? The answer turned out to be shorter than I expected.

Size on disk predicts nothing

Candidate	Packages	vendor	Files	Loaded per request	Peak memory	composer install
Phalcon a C extension — nothing to install	0	0 MB	12	7	502 kB	0.2 s
Slim	12	0.9 MB	229	79	398 kB	0.5 s
CodeIgniter	3	4.6 MB	781	96	535 kB	0.6 s
Laminas	23	7.7 MB	1,362	269	607 kB	0.6 s
Symfony	51	15.8 MB	3,362	224	517 kB	0.9 s
Laravel	76	29.6 MB	6,447	359	703 kB	1.2 s
Yii2 largest vendor, fewest files loaded	25	34.1 MB	2,927	62	815 kB	0.9 s

The most instructive row is Yii2. Its 34.1 MB vendor tree is the largest here — larger than Laravel’s — and yet it loads only 62 files to serve a request. Laravel loads 359, Laminas 269, Symfony 224. Most of what Yii2 writes to disk never sits in the path of a request.

The reverse holds too: CodeIgniter ships with just 3 composer packages, the leanest dependency tree in the field. That leanness does not turn into speed.

Files per request does not predict it either

Load the interactive chart

Loads ~60 kB of JavaScript for tooltips and cursor readings. The data table below is always open.

Data table

get_included_files() on a warm container, single request

Series	Phalcon	Yii2	Slim	CodeIgniter	Symfony	Laminas	Laravel
files loaded	7	62	79	96	224	269	359

The chart is drawn in the browser; the table below carries the same data.

Put the load figures next to this table and the relationship falls apart. CodeIgniter loads 96 files per request and serves 6,431 req/s; Symfony loads 224 and serves 13,067. The framework opening more than twice as many files serves more than twice as many requests.

The reason is opcache. With validate_timestamps=0 a file is compiled once and stays in shared memory, so on later requests “loading” it means binding to ready opcode rather than reading from disk. File count is therefore cheap on the warm path. To see where it is expensive, you have to empty the opcache.

Where the difference actually is: the cold first request

Load the interactive chart

Loads ~60 kB of JavaScript for tooltips and cursor readings. The data table below is always open.

Data table

Fresh container, first HTTP request, front controller to response

Series	Phalcon	Slim	Yii2	CodeIgniter	Laminas	Symfony	Laravel
cold first request	2.2 ms	7.9 ms	17.4 ms	22.2 ms	27.7 ms	35.7 ms	72.2 ms

The chart is drawn in the browser; the table below carries the same data.

The ratio between cold and warm gives the compile bill directly:

Candidate	Cold first request	Warm request	Ratio
Phalcon	2.2 ms	0.41 ms	5×
Slim	7.9 ms	0.35 ms	23×
Yii2	17.4 ms	0.45 ms	39×
CodeIgniter	22.2 ms	1.04 ms	21×
Laminas	27.7 ms	0.79 ms	35×
Symfony	35.7 ms	0.69 ms	52×
Laravel	72.2 ms	1.26 ms	57×

In a pool of eight workers that means close to half a second of accumulated latency across the first eight requests after a Laravel deploy. On a busy site it shows up as a brief spike and disappears; on a page that gets a handful of visitors a day, the first visitor pays it every time.

Peak memory: the order nobody expects

The most inverted result in the table is memory. Laravel, which loads the most files per request (359), peaks at 703 kB; Yii2, which loads the fewest (62), is the highest in the field at 815 kB. File count misleads here too: memory depends on how many objects those files construct, not on how many were opened.

Slim is lowest at 398 kB, as expected from how few objects it builds. Phalcon’s 502 kB is the interesting one: it runs almost no PHP code, yet still constructs its objects in PHP’s memory space.

Findings that did not fit the table

1. Phalcon’s composer install takes 0.2 s because there is nothing to install. The project has 12 files and its composer.lock carries an empty package list; the framework is a C extension compiled into the PHP binary. The trade is on the other side: upgrading is not composer update, it is compiling an extension on the server.
2. ext-psr forced the shared image to fork. Phalcon requires it, and with it loaded Symfony is fatal on PHP 8.4. Phalcon runs on its own runtime image; the PHP version, opcache settings, nginx and php-fpm pool are byte-identical, and only those two extensions differ.
3. ext-mysqli is installed for all seven because CodeIgniter 4 has no PDO driver. The other six never use it; it is there so the extension set stays identical.
4. Laminas’s official skeleton has not been released for PHP 8.4. laminas-mvc-skeleton 2.4.0 declares ~8.1.0 || ~8.2.0 || ~8.3.0 and refuses to install without --ignore-platform-req=php. So the 23 packages and 1,362 files in the table were installed on a version that is not officially supported.
5. Most of Yii2’s 34.1 MB is bower and npm assets. The basic skeleton pulls jQuery and Bootstrap into the vendor tree; none of it is used by the routes in this measurement.
6. composer install times were measured with a warm package cache. On a cold cache the figures would track network speed and say nothing about the framework. The median of three runs is reported; this is the only noisy column in the table.
7. opcache preload was not enabled for any candidate. CodeIgniter ships a preload.php, and there are well-known recipes for Laravel and Symfony. Enabling it changes the cold-first-request figures fundamentally — but it is not a floor all seven share, so it was left out of scope. It deserves its own measurement.
8. Image sizes do not separate the frameworks. They range from 486 to 518 MB and nearly all of that is the shared PHP base image; the vendor tree is small beside it. That is why the column is not in the table, though it is in the raw data.