PHP Reference & Cheatsheet — Complete Guide

DodaTech Updated 2026-06-06 6 min read

In this tutorial, you'll learn about PHP Reference & Cheatsheet. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

Learning Path

flowchart LR
    A["Php Overview"] --> B["Core Concepts"]
    B --> C["Intermediate Topics"]
    C --> D["Advanced Topics"]
    D --> E["Practical Applications"]
    A --> F["You Are Here"]
    style F fill:#f90,color:#fff

A comprehensive PHP reference for daily development — syntax, data types, built-in functions, database access, security patterns, and common configurations.

PHP Tags & Syntax

<?php       // Standard opening tag (always works)
<?=         // Short echo tag — same as <?php echo
//         // Single-line comment
#          // Also single-line comment
/* */      // Multi-line comment
/** */     // DocBlock comment for documentation
;          // Statement terminator (required)

Variables & Superglobals

$var        // Variable (must start with $)
$_SERVER    // Server & execution environment info
$_GET       // URL query parameters
$_POST      // HTTP POST data
$_REQUEST   // GET + POST + COOKIE combined
$_SESSION   // Session variables
$_COOKIE    // HTTP cookies
$_FILES     // File upload data
$_ENV       // Environment variables
$GLOBALS    // All global scope variables

Data Types

Type	Example	Check function
`string`	`"hello"`, `'world'`	`is_string()`
`int`	`42`, `-5`	`is_int()`
`float`	`3.14`	`is_float()`
`bool`	`true`, `false`	`is_bool()`
`array`	`[1, 2]`, `["key" => "val"]`	`is_array()`
`object`	`new ClassName()`	`is_object()`
`null`	`null`	`is_null()`

Control Flow Quick Reference

if (condition) { } else { }
if (condition): else: endif;          // Alternative syntax
switch (expr) { case val: break; }
match (expr) { val => result, }       // PHP 8+, returns value
for ($i = 0; $i < n; $i++) { }
foreach ($array as $value) { }
foreach ($array as $key => $value) { }
while (condition) { }
do { } while (condition);
break n;    // Exit n levels
continue n; // Skip n levels

String Functions

Function	Description
`strlen($s)`	String length
`strpos($s, $needle)`	Find position (false if not found)
`substr($s, start, length)`	Extract substring
`str_replace($search, $replace, $subject)`	Replace all occurrences
`strtolower($s)` / `strtoupper($s)`	Case conversion
`trim($s)`	Strip whitespace from both ends
`explode($delim, $s)`	String to array
`implode($glue, $arr)`	Array to string
`htmlspecialchars($s)`	Escape HTML entities (XSS prevention)
`number_format($num, 2)`	Format with comma separators

Array Functions

Function	Description
`count($arr)`	Element count
`array_push($arr, ...)` / `array_pop($arr)`	Stack operations
`in_array($needle, $arr)`	Check if value exists
`array_key_exists($key, $arr)`	Check if key exists
`array_keys($arr)` / `array_values($arr)`	Get all keys/values
`array_merge($a, $b)`	Merge arrays
`array_map($callback, $arr)`	Transform each element
`array_filter($arr, $callback)`	Filter elements
`array_reduce($arr, $callback, $init)`	Reduce to single value
`array_unique($arr)`	Remove duplicates
`array_reverse($arr)`	Reverse order
`sort($arr)` / `asort($arr)` / `ksort($arr)`	Sorting variants
`array_slice($arr, offset, len)`	Extract portion

PDO Database

// Connect
$pdo = new PDO("mysql:host=$host;dbname=$db;charset=utf8mb4", $user, $pass, [
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES => false,
]);

// Prepared statements (SAFE)
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$id]);
$row = $stmt->fetch();
$rows = $stmt->fetchAll();

$stmt = $pdo->prepare("INSERT INTO users (name, email) VALUES (:name, :email)");
$stmt->execute(["name" => $name, "email" => $email]);
$id = $pdo->lastInsertId();

// Transactions
$pdo->beginTransaction();
$pdo->commit();
$pdo->rollBack();

Sessions & Cookies

session_start();                            // Before any output
$_SESSION["key"] = "value";                 // Set session var
unset($_SESSION["key"]);                    // Remove
session_destroy();                          // Destroy all
session_regenerate_id(true);                // After login

setcookie("name", "value", time()+86400, "/", "", true, true);
$_COOKIE["name"] ?? null;                   // Read cookie

Security Best Practices

// Password hashing
$hash = password_hash($password, PASSWORD_BCRYPT, ["cost" => 12]);
password_verify($password, $hash);
password_needs_rehash($hash, PASSWORD_BCRYPT, ["cost" => 12]);

// XSS prevention
htmlspecialchars($userInput, ENT_QUOTES, "UTF-8");

// SQL injection prevention
// Use PDO prepared statements exclusively

// CSRF token
bin2hex(random_bytes(32));  // Generate token

// File upload safety
finfo_file(finfo_open(FILEINFO_MIME_TYPE), $tmpName);
move_uploaded_file($tmpName, $dest);

Common PHP ini Directives

display_errors = On        ; Show errors (dev only)
error_reporting = E_ALL    ; Report all errors
max_execution_time = 30    ; Max seconds
memory_limit = 128M        ; Per-script memory
upload_max_filesize = 2M   ; Max upload size
post_max_size = 8M         ; Max POST size
date.timezone = UTC        ; Default timezone

Common Mistakes Beginners Make

1. Skipping the Fundamentals

Many beginners jump straight to advanced topics without mastering the basics. Take time to understand the core concepts before moving on.

2. Not Practicing Enough

Reading tutorials without writing code leads to shallow understanding. Code along with every example and experiment on your own.

3. Ignoring Error Messages

Error messages tell you exactly what went wrong. Read them carefully — they usually point to the line and type of issue.

4. Copy-Pasting Without Understanding

It's tempting to copy code from tutorials, but typing it yourself and understanding each line builds real skill.

5. Giving Up Too Early

Every developer hits frustrating bugs. Take breaks, ask for help, and remember that struggling is part of learning.

FAQ

What is Php Reference?

: Php Reference refers to the core concepts and practices used to build and manage modern web applications. Understanding it is essential for web developers.

Do I need prior experience to learn Php Reference?

: Basic familiarity with web development concepts helps, but Php Reference can be learned step by step even as a beginner.

How long does it take to learn Php Reference?

: With consistent practice, you can grasp the fundamentals in a few days to a week. Mastery takes ongoing practice and real-world projects.

Where can I use Php Reference in real projects?

: Php Reference is used in a wide range of applications — from simple websites to complex enterprise systems, depending on the specific tools and technologies involved.

What are common tools used with Php Reference?

: The specific tools depend on the technology stack, but version control (Git), package managers, and testing frameworks are commonly used alongside most development topics.

What's Next

Lesson	Description
{{< ref "laravel.md" >}}	Modern PHP framework
{{< ref "symfony.md" >}}	Enterprise PHP framework
{{< ref "../nodejs/reference.md" >}}	Node.js reference
MySQL	Database reference
Laravel	Framework reference

What's Next

Congratulations on completing this Php Reference tutorial! Here's where to go from here:

Practice daily — Consistency is more important than long study sessions
Build a project — Apply what you learned by building something real
Explore related topics — Check out other tutorials in the same category
Join the community — Discuss with other learners and share your progress

Remember: every expert was once a beginner. Keep coding!

← Previous PHP Advanced — OOP, Sessions, PDO Database & Error Handling Next → Laravel PHP Framework Guide — Modern MVC Development

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