In PHP, logical operators are used to combine or evaluate conditions, and the main operators include &&, and, ||, or, ! and xor. 1. The difference between && and is the priority. && is higher than the assignment operator, while and is lower than the assignment operator, so the behavior is different when combining assignment; 2.|| and or also have similar priority differences, || takes precedence over assignment, while or is processed after assignment; 3.! operator is used to inverse boolean values, often used to check whether the conditions are false, and it is recommended to wrap complex expressions in brackets to ensure correct application; 4.xor returns true only when exactly one of the two values ??is true, which is suitable for mutex condition judgment; 5. The best practice is to use && and || first to obtain more predictable behavior, use brackets appropriately to improve readability, avoid mixing too many ungrouped operators, and use xor carefully to avoid misunderstandings.

In PHP, logical operators are used to combine or evaluate conditions — especially in control structures like if , else if , and loops. The main ones you'll use are && (and), || (or), ! (not), and their lowercase counterparts and , or , and xor . While they work similarly, there's one key difference: operator precedence. That affects how expressions are grouped and evaluated.

Here's a practical breakdown of how to use them effectively.

Understanding && vs and

Both && and and check whether two conditions are true. The only difference is precedence .

• && has higher precedence than assignment operators.
• and has lower precedence.

This matters when you're combining assignments with logic:

 $a = true && false;
var_dump($a); // false

$b = true and false;
var_dump($b); // true — because it evaluates as ($b = true) and then ignores the rest

So unless you're intentionally relying on that behavior, stick with && for consistency and clarity.

How to Use || and or

Like && and and , || and or do similar things but have different precedence levels.

• || is evaluated before assignments.
• or is evaluated after assignments.

Example:

 $c = false || true;
var_dump($c); // true

$d = false or true;
var_dump($d); // false — again, because it does $d = false first

In most cases, you'll want || because it behaves more predictably in conditions.

When to Use ! (NOT)

The ! operator simply flips a boolean value.

Use it to check if something is not true:

 if (!$isLoggedIn) {
    echo 'Please log in.';
}

It's commonly used with functions that return boolean values:

 if (!file_exists('data.txt')) {
    echo 'File missing!';
}

Make sure to wrap complex expressions in parentshes when using ! so it applies correctly:

 if (!(is_numeric($input) && $input > 0)) {
    echo 'Input must be a positive number.';
}

Using xor (Exclusive OR)

This one's less common, but handy in specific cases.

xor returns true only when exactly one of the two values ??is true , not both.

Examples:

 var_dump(true xor true); // false
var_dump(true xor false); // true
var_dump(false xor true); // true
var_dump(false xor false); // false

You might use it in forms where the user should select one option from two, but not both. Or in state checks where mutual exclusive matters.

Final Tips

• Prefer && and || over and , or unless you specifically need low-precedence behavior.
• Use parentses liberally to avoid confusion.
• Avoid mixing too many operators without grouping — readability wins.
• Use xor sparingly; it's easy to misinterpret in complex logic trees.

Basically that's it.

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