PHP Interview Questions (Part 2)

Building on the fundamentals of PHP, advancing your expertise requires diving deeper into more complex concepts and real-world scenarios. As interviews for developer roles become increasingly challenging, it’s not enough to know just the basics—you need to demonstrate a strong understanding of advanced PHP topics, best practices, and problem-solving techniques.

This second part of PHP interview questions is crafted to take your preparation to the next level. It covers more in-depth questions that recruiters often ask to evaluate your practical knowledge and coding proficiency. By exploring these questions and their detailed answers, you’ll strengthen your technical foundation, gain confidence in handling tricky interview situations, and position yourself as a well-rounded PHP developer ready to tackle modern web development challenges.

What are the main types of operators in PHP and how do they behave

Operators are symbols used to perform operations on variables and values

Core types

• Arithmetic + – * / % **

echo 2 + 3; // 5
echo 2 ** 3; // 8

• Assignment
  = += -= *= /= .=

$x = 5;
$x += 2; // 7

• Comparison
  == === != !== > < >= <= <=>

var_dump(10 == "10");  // true
var_dump(10 === "10"); // false

• Logical
  && || !

var_dump(true && false); // false

• String
  . .=

echo "Hello " . "World";

• Increment / Decrement
  ++ —

$x = 5;
echo ++$x; // 6

Key point

• == compares value
• === compares value and type

Common mistake

Using == instead of ===
This can cause unexpected results due to type juggling

Quick check

var_dump(0 == false);   // true
var_dump(0 === false);  // false

What is the shorthand if statement in PHP and when would you use it

Shorthand if is a compact way to write conditional logic

Ternary operator

• condition ? value_if_true : value_if_false

$age = 20;
$status = ($age >= 18) ? "Adult" : "Minor";

Short ternary (Elvis operator)

• expression ?: default_value
• returns expression if truthy, otherwise default

$name = $input ?: "Guest";

Null coalescing operator

• checks if variable exists and is not null

$name = $_GET['name'] ?? "Guest";

Key differences

• ?: checks truthy or falsy
• ?? checks existence and null only

Common mistake

Using ?: when you actually need ??

$val = 0 ?: 100;   // 100  
$val = 0 ?? 100;   // 0

When should you use shorthand if

• Simple conditions
• Default values
• Clean code in assignments

Avoid it in complex logic
it reduces readability

What happens if you remove the break statement from a case in a switch in PHP

Execution continues into the next case

• This is called fall-through
• PHP does not stop at the matched case
• It keeps running the following cases until it finds a break or reaches the end

Example

$day = "Monday";

switch ($day) {
    case "Monday":
        echo "Start of week ";
    case "Tuesday":
        echo "Work day ";
        break;
    case "Wednesday":
        echo "Mid week ";
}

Output

Start of week Work day

Why this can be dangerous

• You may execute unintended code
• Bugs become hard to detect

When is it useful

• When multiple cases share the same logic

switch ($day) {
    case "Saturday":
    case "Sunday":
        echo "Weekend";
        break;
}

Key idea

• With break → stop after match
• Without break → continue execution

Quick check

What will this print

$x = 1;

switch ($x) {
    case 1:
        echo "One ";
    case 2:
        echo "Two ";
}

One Two

What is the match expression in PHP and when should you use it

match is a modern alternative to switch introduced in PHP 8

• It returns a value
• It uses strict comparison ===
• It does not allow fall-through
• Each case must return a result

Basic example

$status = 200;

$message = match ($status) {
    200 => "OK",
    404 => "Not Found",
    500 => "Server Error",
};

Key differences from switch

• match uses strict comparison
  no type juggling
• no break needed
  each case is isolated
• returns a value directly
  cleaner for assignments
• throws error if no match found
  unless you define default

$result = match ($x) {
    1 => "One",
    default => "Other",
};

When should you use match

• When mapping values to results
• When you need clean return logic
• When you want strict type safety
• When you want to avoid fall-through bugs

When not to use match

• Complex logic with multiple statements
• Cases that need side effects
• Traditional flow control scenarios

Common mistake

Forgetting default

• can cause UnhandledMatchError

Quick check

$x = "1";

echo match ($x) {
    1 => "int",
    "1" => "string",
};

Output
string

Why
because match uses strict comparison

What is the difference between break and continue in loops in PHP

They control loop flow in different ways

What does break do

• Stops the loop completely
• Execution moves to the next line after the loop

for ($i = 1; $i <= 5; $i++) {
    if ($i == 3) {
        break;
    }
    echo $i;
}

Output
1 2

What does continue do

• Skips current iteration
• Moves to the next loop iteration

for ($i = 1; $i <= 5; $i++) {
    if ($i == 3) {
        continue;
    }
    echo $i;
}

Output
1 2 4 5

Key difference

• break → exit loop
• continue → skip one iteration

Advanced use

You can control nested loops

break 2;     // exits two levels  
continue 2;  // skips to next iteration of outer loop  

Common mistake

Using continue when you want to stop loop entirely

Quick check

What will this print

for ($i = 1; $i <= 3; $i++) {
    if ($i == 2) continue;
    echo $i;
}

Output
1 3

What is the difference between while and do while in PHP

The difference is when the condition is checked

while loop

• Checks condition first
• Executes only if condition is true

$i = 1;

while ($i < 1) {
    echo $i;
    $i++;
}

Output
nothing

do while loop

• Executes first
• Then checks condition

$i = 1;

do {
    echo $i;
    $i++;
} while ($i < 1);

Output
1

Key difference

• while → may run zero times
• do while → runs at least once

When to use each

• while
  when you are not sure the condition is true
• do while
  when you must execute the code at least once

Common mistake

Expecting while to run at least once
it will not if condition is false

Quick check

$i = 0;

while ($i > 0) {
    echo "A";
}

do {
    echo "B";
} while ($i > 0);

Output
B

Continue Your PHP Interview Preparation

If you found this guide helpful, don’t miss the rest of our comprehensive PHP interview series:

• 👉 PHP Interview Questions Part 1
• 👉 PHP Interview Questions Part 2
• 👉 PHP Interview Questions Part 3
• 👉 PHP Interview Questions Part 4

By going through the full series, you’ll build a strong foundation in PHP and be fully prepared to tackle interviews with confidence.