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I was reading a piece of code and saw that the author of the code uses the following if statement

if ( 'string' == $var )

where as I always use

if ( $var == 'string' )

What i'm wondering is if this has any other function except for style/looks. Is comparing a $var to a 'string' quicker/slower than a 'string' to a $var?

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  • stackoverflow.com/questions/29910258/… Commented May 4, 2015 at 11:23
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    It's called yoda condition! Commented May 4, 2015 at 11:23
  • $var ='string' ; if ( 'string' == $var ){ echo "HI"; } No differenece echoes HI Commented May 4, 2015 at 11:23
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    The difference is if you make a typo and use = instead of == Commented May 4, 2015 at 11:24
  • Also see: stackoverflow.com/a/28840422/3933332 Commented May 4, 2015 at 11:25

1 Answer 1

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Why if( constant == variable ) is preferred instead of if ( variable == constant )

Here is an answer to your question. This helps in debugging if you miss an equal sign.

Because that form makes it harder to introduce a bug by forgetting one of the equals signs. Imagine if you did this:

if (k = 5) This was intended as a comparison, but it's now an assignment! What's worse, it is legal, and it will mess up your program in multiple ways (the value of k is changed, and the conditional always evaluates to true).

Contrast this with

if (5 = k) This is not legal (you cannot assign to a literal) so the compiler will immediately flag it as an error.

in the words of Hanky 웃 Panky in comments:

They are both equivalent but 'string'==$var is a better approach because it helps in debugging if you miss an equal sign.

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3 Comments

This is a comment not an answer!
It would have been a very nice answer had you improved your statement to make it complete. Something like They are both equivalent but 'string'==$var is a better approach because it helps in debugging if you miss an equal sign.
Even though it's not an answer to my question it is in fact what I secretly was looking for without realizing it myself. I've always been using the k = 5 notation but do realize now that apparently it's bad practice or well the latter is preferred. I'll see if I can get myself to switching over to 5 = k :)

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