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phploopsfor-loopincrementoperator-keyword
Mert S. Kaplan
Mert S. Kaplan

Reputation: 1126

Why is addition not working instead of increment operator in for loop in PHP?

I needed to increment the for loop by 7 by 7 and used the $x + 7 method as below. However, it didn't work.

for ($x = 1; $x <= 31; $x + 7) { 
    echo $x ."\n";
}

I solved the problem by redefining the variable as below but I am still wondering why the first method is not working.

for ($x = 1; $x <= 31; $x += 7) { 
    echo $x ."\n";
}

I usually use the $x++ method to increase the value. Why is $x + 7 different?

You can try: https://glot.io/snippets/g16a4it4il

Upvotes: 0

Views: 302

Answers (2)

kmoser
kmoser

Reputation: 9273

$x + 7 does not alter x. It simply evaluates to 7 more than $x. To add 7 to $x, you can either:

$x += 7

or

$x = $x + 7

$x++ increments $x by 1. It is roughly equivalent to $x = $x + 1 or $x += 1. (Although when used in an expression, $x++ evaluates to the value of $x before the increment happens; for further information see What's the difference between ++$i and $i++ in PHP?)

Upvotes: 2

Ben Chamberlin
Ben Chamberlin

Reputation: 731

The for loop works by changing $x every iteration until $x <= 31 is no longer true.

$x + 7 doesn't change $x, so it'll always remain 1

Upvotes: 1

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