PHP Memory Management Tips

0-PHP-MEMORY-MANAGE.MD

PHP MEMORY MANAGEMENT TIPS

https://code-boxx.com/php-memory-management/

LICENSE

Copyright by Code Boxx

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

1-db-line-by-line.php

<?php
// (A) DATABASE SETTINGS
define("DB_HOST", "localhost");
define("DB_NAME", "test");
define("DB_CHARSET", "utf8mb4");
define("DB_USER", "root");
define("DB_PASSWORD", "");

// (B) CONNECT TO DATABASE
$pdo = new PDO(
  "mysql:host=".DB_HOST.";dbname=".DB_NAME.";charset=".DB_CHARSET,
  DB_USER, DB_PASSWORD, [
  PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
  PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
]);

// (C) PREPARE SQL
$stmt = $pdo->prepare("SELECT * FROM `TABLE`");
$stmt->execute();

// (D) BAD - FETCH ALL AT ONCE
// $results = $stmt->fetchAll();
// foreach ($results as $r) { print_r($r); }

// (E) PREFERRED - FETCH LINE-BY-LINE
while ($r = $stmt->fetch()) { print_r($r); }

// (F) CLOSE DATABASE CONNECTION
if ($stmt !== null) { $stmt = null; }
if ($pdo !== null) { $pdo = null; }

// (G) PEAK MEMORY USED
echo "PEAK USAGE - " . memory_get_peak_usage();

2-file-line-by-line.php

<?php
// (A) TARGET FILE
$source = "FILE.txt";

// (B) BAD - READ EVERYTHING INTO A STRING
// $contents = file_get_contents($source);
// print_r($contents);

// (C) PREFERRED - READ LINE-BY-LINE
$handle = fopen($source, "r") or exit("Failed to open " . $source);
while ($line = fgets($handle)) { echo $line; }
fclose($handle);

// (D) PEAK MEMORY USED
echo "PEAK USAGE - " . memory_get_peak_usage();

3-reduce-var.php

<?php
// (A) BAD - INTRODUCE NEEDLESS VARIABLES
$varA = 123;
$varB = 234;
$varC = $varA + $varB;

// (B) IF $VARA $VARB ARE NOT USED ANYWHERE ELSE - DON'T INTRODUCE THEM
$varC = 123 + 234;

// (C) PEAK MEMORY USED
echo "PEAK USAGE - " . memory_get_peak_usage() . "<br>";

4-manual-unset.php

<?php
// (A) TEMPORARY VARIABLES FOR CALCULATIONS
$varA = 123;
$varB = 234;
$varC = $varA + $varB;

// (B) MANUALLY REMOVED
unset($varA);
unset($varB);
gc_collect_cycles();

5-direct-output.php

<?php
// (A) DATABASE SETTINGS
define("DB_HOST", "localhost");
define("DB_NAME", "test");
define("DB_CHARSET", "utf8mb4");
define("DB_USER", "root");
define("DB_PASSWORD", "");

// (B) CONNECT TO DATABASE
$pdo = new PDO(
  "mysql:host=".DB_HOST.";dbname=".DB_NAME.";charset=".DB_CHARSET,
  DB_USER, DB_PASSWORD, [
  PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
  PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
]);

// (C) HTTP HEADERS
header("Content-Type: application/octet-stream");
header("Content-Transfer-Encoding: Binary");
header("Content-disposition: attachment; filename=\"export.csv\"");

// (D) PREPARE SQL
$stmt = $pdo->prepare("SELECT * FROM `TABLE`");
$stmt->execute();

// (E) BAD - FETCH ALL AT ONCE
// $results = $stmt->fetchAll();
// foreach ($results as $r) { echo implode(",", $r) . "\r\n"; }

// (F) PREFERRED - FETCH & DIRECTLY OUTPUT
while ($r = $stmt->fetch()) { echo implode(",", $r) . "\r\n"; }

// (G) CLOSE DATABASE CONNECTION
if ($stmt !== null) { $stmt = null; }
if ($pdo !== null) { $pdo = null; }

A-track-mem.php

<?php
// (A) GENERATE A LARGE ARRAY
$arr = [];
for ($i=0; $i<99999; $i++) { $arr[] = $i; }

// (B) MEMORY USAGE WITH ARRAY IN MEMORY
echo "<strong>WITH LARGE ARRAY IN MEMORY</strong><br>";
echo "Current usage: " . memory_get_usage() . " bytes<br>";
echo "Peak usage: " . memory_get_peak_usage() . " bytes<br><br>";

// (C) MEMORY USAGE AFTER ARRAY IS REMOVED
unset($arr);
echo "<strong>AFTER ARRAY IS REMOVED</strong><br>";
echo "Current usage: " . memory_get_usage() . " bytes<br>";
echo "Peak usage: " . memory_get_peak_usage() . " bytes";

B-track-time.php

<?php
// (A) START TIMING
$time = microtime(true);

// (B) GENERATE A LARGE ARRAY
$arr = [];
for ($i=0; $i<99999; $i++) { $arr[] = $i; }

// (C) TOTAL TIME TAKEN
$time = microtime(true) - $time;
echo "Time taken - $time secs";