Global Function Style vs OOP Evolution

TL;DR

Explanation

PHP 4 was primarily procedural: functions like mysql_query(), ereg(), split() in global scope, state managed through global variables, no namespaces, everything in include files. PHP 5 introduced proper OOP (classes with visibility, interfaces, abstract classes). PHP 7 added scalar types. Modern PHP is primarily OOP with namespaces and Composer, but the global function library remains (date(), array_map(), file_get_contents()). Legacy codebases often mix both — procedural logic with OOP classes. Migration path: wrap procedural code in classes, add namespaces, replace mysql_ with PDO, use Composer autoloading.

Common Misconception

Why It Matters

Common Mistakes

• Wrapping every function in a class unnecessarily — global functions are fine for pure utility.
• Not namespacing custom global functions — use namespaces to avoid collisions.
• Keeping mysql_ extension calls instead of migrating to PDO.

Code Examples

// PHP 4 style — global state, no OOP:
global $db;
$result = mysql_query('SELECT * FROM users', $db);
while ($row = mysql_fetch_array($result)) {
    echo $row['name'];
}

// Modern — OOP with PDO:
class UserRepository {
    public function __construct(private PDO $pdo) {}

    public function findAll(): array {
        return $this->pdo->query('SELECT * FROM users')->fetchAll();
    }
}

References

• ↗ https://www.php.net/manual/en/history.php.php

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