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Q:

What is the order of evaluation for different types of expressions in PHP?

Hello everyone,

I am new to PHP and I have a question about the order of evaluation for different types of expressions in PHP. I have been trying to find information about this, but I am quite confused. Can someone please help me understand the order of evaluation for different types of expressions in PHP?

I understand that PHP evaluates expressions from left to right, but I am not sure about the specific order for different types of expressions. For example, when it comes to arithmetic operations, does PHP evaluate multiplication before addition, or vice versa?

I have also seen expressions with multiple operators, like logical expressions or comparison expressions. In these cases, I am not sure how PHP determines which operator to evaluate first.

It would be really helpful if someone could provide me with some examples or explain the order of evaluation for different types of expressions in PHP. Additionally, if there are any important considerations or exceptions to the order of evaluation, I would appreciate knowing those as well.

Thank you in advance for your help!

All Replies

mike.christiansen

Hey folks,

I've been working with PHP for quite some time now, and I'd like to share my personal experience regarding the order of evaluation for different types of expressions in PHP.

When it comes to arithmetic operations, PHP follows the principle of operator precedence. This means that multiplication, division, and modulus operations are evaluated before addition and subtraction. For instance, in an expression like 10 + 5 * 2, PHP will first multiply 5 and 2, resulting in 10, and then add it to 10, yielding a final value of 20.

Now, let's talk about logical expressions. PHP uses short-circuit evaluation, just like many other programming languages. This means that if the outcome of an expression can be determined by evaluating the leftmost part, PHP won't evaluate the remaining part. So, if you have an expression like $a || $b, and $a is true, PHP won't bother checking the value of $b since the final result is already guaranteed to be true.

Comparison expressions also follow a straightforward order of evaluation in PHP. Multiple comparison operators in a single expression are evaluated from left to right. For instance, in an expression like $x > $y && $y < $z, PHP will first evaluate $x > $y, and then proceed to evaluate $y < $z.

Although PHP has a clear order of evaluation, it's crucial to remember that parentheses can be used to explicitly define the desired order. Any expressions within parentheses are evaluated first, allowing you to control the priority of operations.

If you have any further questions, feel free to ask. I'm here to help!

bschaden

Hey there,

In my personal experience with PHP, the order of evaluation for different types of expressions is quite straightforward once you get the hang of it.

For arithmetic operations, PHP follows the typical rules of mathematics. Multiplication and division are evaluated before addition and subtraction. So, if you have an expression like 2 + 3 * 4, PHP will first evaluate 3 * 4 (which is 12) and then add 2 to it, resulting in 14.

When it comes to expressions with logical operators, PHP uses short-circuit evaluation. This means that if the outcome of the expression can be determined by evaluating the first operand, PHP won't evaluate the second operand. For example, in an expression like $a && $b, PHP will first evaluate $a, and if $a is false, it won't even bother evaluating $b, since the entire expression is already guaranteed to be false.

Comparison operators, on the other hand, have an order of evaluation from left to right, just like other expressions in PHP. So, in an expression like $x > $y && $y > $z, PHP will first evaluate $x > $y and then move on to evaluate $y > $z.

It's important to note that parentheses can be used to override the default order of evaluation. Anything within parentheses is always evaluated before other parts of the expression. This allows you to control the order in which operations are performed.

I hope this helps! Feel free to ask further questions if you have any.

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