PHP Check if static variable has been declared or initialized?

Question

I want to check if a static variable has been declared/initialized previously, e.g. if a function with a static variable is being run for the first time. See the following example code:

function init_i (){
    // check if $i is set??
    if(isset($i)) echo '$i is static and is set ';


    static $i=0;
    $i++;
    echo "$i<br>";
}

function run_init(){
    init_i();
}

run_init(); //output 1
run_init(); //should output $i is static and is set 2
run_init(); //should output $i is static and is set 3
run_init(); //should output $i is static and is set 4
run_init(); //should output $i is static and is set 5

The problem is that isset($i) never seems to prove true even though it is a static variable. How do I check static $i has already been set?

nice ass · Accepted Answer · 2014-01-04 03:02:02Z

5

Just omit out the default value, and it will be null:

static $i;

// check if $i is set??
if(isset($i)){
  echo '$i is static and is set ';
}else{
  // first call, initialize...
  $i = 0;
}

...

isset() returns TRUE if variable is set and not null.

I don't get what's your reasoning behind this, because you can just check the value is the initial value (0) and you know that's the first call...

answered Jan 4, 2014 at 3:02

nice ass

16.8k8 gold badges54 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user139301 Over a year ago

The point is to know if the function has been run before or if it is the first time. I want the function to behave differently if it is being used in a loop. I did not think about separating variable assignment during declaration.

deceze Over a year ago

@user Sounds like a bad idea. Functions should not behave differently in a loop or elsewhere. Research "idempotence".

KorreyD · Accepted Answer · 2014-01-04 12:26:57Z

2

you can do

function init_i (){
    static $i=0;

    // check if $i is set??
    if ( $i != 0 )
         echo '$i is static and is set ';
    $i++;
    echo "$i<br>";
}

edited Jan 4, 2014 at 12:26

answered Jan 4, 2014 at 3:00

KorreyD

1,2948 silver badges15 bronze badges

1 Comment

KorreyD Over a year ago

oops you're right. i had 2 echo 'i is static and is set' lines in there giving me false results. i will remove that 2nd function from my answer

Nambi · Accepted Answer · 2014-01-04 06:36:55Z

0

check the condition after declared the static variable

static $i=0;
if(isset($i)){
 echo '$i is static and is set ';
}else{
$i=0;
}

edited Jan 4, 2014 at 6:36

answered Jan 4, 2014 at 2:54

Nambi

12k4 gold badges40 silver badges50 bronze badges

2 Comments

user139301 Over a year ago

But then the first time function is run, the if statement will prove true. I would like it to prove true the second time and beyond.

Nambi Over a year ago

yeah check it in else condition as well

Collectives™ on Stack Overflow

PHP Check if static variable has been declared or initialized?

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related