CODEWITHSUNDEEP
phpperformanceif-statement
Oliver Holmberg
Oliver Holmberg

Reputation: 731

If (x OR y) Performance

I have a performance related question regarding how PHP evaluates the OR operator in a conditional.

I have a conditional that calls 2 functions, both returning booleans:

The first is a simple, fast function - simpleFunction()

The second is a more intensive function that queries the DB - intensiveFunction()

I could write the conditional like this, so that if the first, simple function returned TRUE, the second more intense function would not be executed:

if ( simpleFunction() ) {
   // Do Stuff
} elseif ( intensiveFunction() ) {
   // Do the same stuff (redundant code)
}

My question is, when using and OR operator in a PHP conditional, if the first condition (on the left of the operator) is TRUE, will the second function (on the right side of the operator) be executed?

if ( simpleFunction() || intensiveFunction() ) {
    //Do Stuff
}

This conditional will be running inside a loop, so I would like to avoid running intensiveFunction() on every iteration.

Upvotes: 0

Views: 107

Answers (3)

Langdi
Langdi

Reputation: 229

Additionally compare this script testing the various logical operators:

<pre>
<?php
function test($bool) {
    echo "I was executed\n";

    return $bool;
}

echo "<b>||-Operator</b>\n";
if (test(true) || test(true)) {
    ;
}

echo "<b>|-Operator</b>\n";
if (test(true) | test(true)) {
    ;
}

echo "<b>or-Operator</b>\n";
if (test(true) or test(true)) {
    ;
}

echo "<b>&&-Operator</b>\n";
if (test(false) && test(true)) {
    ;
}

echo "<b>&-Operator</b>\n";
if (test(false) & test(true)) {
    ;
}

echo "<b>and-Operator</b>\n";
if (test(false) and test(true)) {
    ;
}
?>
</pre>

Output:

||-Operator
I was executed
|-Operator
I was executed
I was executed
or-Operator
I was executed
&&-Operator
I was executed
&-Operator
I was executed
I was executed
and-Operator
I was executed

Note that | and & always execute the second part even when the output can't be true (&-Operator) anymore or can't become false (|-Operator) anymore.

Upvotes: 2

Oliver Holmberg
Oliver Holmberg

Reputation: 731

As Neal pointed out, I should have just tested this:

$hasRun = 'Intesive Function Has NOT Run';

function simpleFunction() {
    return TRUE;    
}

function intensiveFunction() {
    $hasRun = 'Intesive Function Has Run';  
    return TRUE;
}

if ( simpleFunction() || intensiveFunction() ) {
    echo $hasRun;   
}

//Result: Intesive Function Has NOT Run function

So yes, once the first condition returns TRUE the conditional exits and the second condition is not evaluated.

Upvotes: 0

Naftali
Naftali

Reputation: 146310

I believe that once a truthy is found in an or operation, then the statement ends and returns true,

Whereas in an and operation, it runs until it finds a falsey.

Upvotes: 6

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