Migrating from PHP 5.x to PHP 7 and 8

Also Known As

TL;DR

Explanation

Migrating from PHP 5.x to 7/8 involves several categories. Removed: mysql_* extension, ereg_* functions, magic_quotes_gpc, safe_mode, call-time pass-by-reference, and mcrypt. Changed: strict comparison semantics (0 == 'string' is now false in PHP 7), error handling (many fatals become catchable Errors), constructor-style constructors. Tools: Rector auto-fixes most mechanical changes, phpcs with PHPCompatibility standard flags version-specific issues. Running tests on a PHP 7 Docker container before deploying is the safest approach.

Common Misconception

Why It Matters

Common Mistakes

• Not running the full test suite on PHP 7 before deploying
• Ignoring Rector in favour of manual migration
• Not checking third-party packages for PHP 7 compatibility
• Leaving mysql_* calls for later and being surprised by fatal errors in production

Code Examples

// PHP 5 patterns that break in PHP 7:
ereg('^[a-z]+$', $input); // Fatal — ereg removed
mysql_query($sql); // Fatal — mysql_ removed
list($a, $b) = $arr; // OK but some list() behaviour changed

// PHP 7 equivalents:
preg_match('/^[a-z]+$/', $input);
$pdo->prepare($sql)->execute();
[$a, $b] = $arr; // Short list syntax

// Run Rector before upgrading:
// vendor/bin/rector process --dry-run

References

• ↗ https://www.php.net/manual/en/migration70.incompatible.php
• ↗ https://github.com/rectorphp/rector

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