10 Must-Know PHP Functions Every Developer Should Use
Do you want to write better PHP code? You should use these ten straightforward yet effective PHP functions in practical projects.
We all know PHP can do a lot, but sometimes it's the simple functions that save the day. However, as developers, we frequently find ourselves repeatedly searching for the same information on Google (I know I do). I therefore created this list of ten PHP functions that I have utilized in practically all of my projects, whether they are REST APIs, admin dashboards, or basic contact forms.
These functions aren't fancy or complicated. They will simplify your PHP life and are dependable and practical. Let’s get started.
1. isset()
Why it’s useful:
This checks if a variable exists and is not null.
Example:
You’re processing a form submission.
if (isset($_POST['email'])) {
$email = $_POST['email'];
}
Real-life use:
Use it before accessing any $_POST or $_GET value to avoid errors.
2. empty()
Why it’s useful:
Checks if a variable is empty ("", 0, null, false, etc.).
Example:
if (empty($_POST['password'])) {
echo "Password is required.";
}
Real-life use:
Validating form fields before saving to database.
3. trim()
Why it’s useful:
Removes extra white space from start and end.
Example:
$name = trim($_POST['name']);
Real-life use:
When users submit forms with spaces — " John " becomes "John".
4. explode()
Why it’s useful:
Converts a string into an array using a delimiter.
Example:
$tags = "php,backend,laravel";
$tagArray = explode(",", $tags);
Real-life use:
Storing tags or skills in a comma-separated format.
5. implode()
Why it’s useful:
Opposite of explode() — combines array into a string.
Example:
$skills = ['PHP', 'MySQL', 'HTML'];
$skillsStr = implode(", ", $skills);
Real-life use:
Displaying stored user skills or CSV export.
6. strtolower() and strtoupper()
Why it’s useful:
Convert string to lowercase or uppercase.
Example:
$email = strtolower($_POST['email']);
Real-life use:
Normalize emails before checking in DB.
7. htmlspecialchars()
Why it’s useful:
Prevents XSS attacks by escaping special characters.
Example:
echo htmlspecialchars($userInput);
Real-life use:
Displaying user-submitted content safely.
8. password_hash() and password_verify()
Why it’s useful:
Safely hash and verify passwords.
Example:
$hash = password_hash($password, PASSWORD_DEFAULT);
Example (Login):
if (password_verify($password, $storedHash)) {
// Login successful
}
Real-life use:
Use this instead of manually encrypting or using MD5/SHA1.
9. file_exists()
Why it’s useful:
Checks if a file is available before using it.
Example:
if (file_exists("uploads/profile.jpg")) {
echo "File is there.";
}
Real-life use:
Before displaying profile images or downloading files.
10. json_encode() and json_decode()
Why it’s useful:
Convert PHP arrays to JSON and vice versa.
Example:
$data = ['name' => 'John', 'age' => 30];
$json = json_encode($data);
Real-life use:
Creating APIs or working with JavaScript frontends.
Bonus: Combine Functions for Better Flow
You can combine multiple functions for smoother logic. Example:
if (isset($_POST['email']) && !empty(trim($_POST['email']))) {
$email = strtolower(trim($_POST['email']));
}
This small block checks, trims, and formats the email in one go — something every dev does daily.
Final Thoughts
Despite their apparent simplicity, these ten functions address significant issues in day-to-day PHP development. These are your mainstays, whether you're creating an API, validating a form, or cleaning up input.
Please bookmark this if you found it useful. Give it to your friends who are developers. Or leave a comment with your preferred PHP function; I may have overlooked some!
