Using PHP here, I decided to read through the manual chapter by chapter and learn new things. So now I've discovered static variables, which seem like an awesome concept, but the way I understand it is:
Static variables are set once and only once per load of the script. They can be changed and incremented but not actually re-set. Usually used in functions to set a value and not have to initialize that variable every time the function runs.
<?php
function count2( $inputNum ) {
static $a = $inputNum;
echo $a++; //Echo and then increment.
}
for ( $i = 0; $i < 10; $i++ ) {
count2(50);
}
?>
I'd expect this to start the static $a var at 50, and increment 11 times. How come I get an error?
The static variable cannot be initialized with another variable, whose value is not known until runtime. You must initialize it with a value known at compile time.
function count2($inputNum) {
// Initialize only once to an integer (non variable, non-expression)
static $a = 0;
if ($a === 0) {
// If $a is still 0, set it to $inputNum
$a = $inputNum;
}
echo $a++;
}
// First run outputs 25
count2(25);
// 25
// Subsequent runs increment
count2(25);
// 26
count2(25);
// 27
Like any other PHP static variable, static properties may only be initialized using a literal or constant; expressions are not allowed. So while you may initialize a static property to an integer or array (for instance), you may not initialize it to another variable, to a function return value, or to an object.
I think you missed that part from the docs (emphasize mine) :)
Few problems off the bat:
count2() 10 times.++ operator because you can't change a static varconstantPerhaps try something like:
<?php
error_reporting(E_ALL);
/* setup */
function set( $input ) {
define( 'A', $input );
}
function tick() {
echo constant( 'A' ) . "
";
}
/* run */
set( 50 );
for($i=0; $i<10; $i++){
tick();
}
?>
This will output:
$ php test.php
50
50
50
50
50
50
50
50
50
50