CODEWITHSUNDEEP
phpcaching
dariush
dariush

Reputation: 3341

does function_exists() cache its queries?

I wonder to know does function_exists() cache its queries internally?

Upvotes: 4

Views: 391

Answers (2)

dariush
dariush

Reputation: 3341

No it doesn't, the following performance tests are confirming the fact:

function function_exists_cached($function_name)
{
    static $cache = array();
    if(isset($cache[$function_name]))
        return $cache[$function_name];
    return ($cache[$function_name] = \function_exists($function_name));

}
$funcs = \array_shift(\get_defined_functions());
$a = new \core\utiles\loadTime;
$times = $tot = 0;
$a->start();
/**
 * None Cached: No cache used here
 **/
for($index = 0; $index<count($funcs); $index++)
{
    foreach($funcs as $func)
    {
        $times++;
        if(\function_exists($func)) ;
    }
}
$s = $a->stop();
$tot+=$s;
echo "<b>None Cached : </b><b><span style='color:green'>#$times</span></b> function check took : $s seconds<br />";
$b = new \core\utiles\loadTime;
$times = 0;
$b->start(); 
/**
 * Fly Cached: An inline cache used here
 **/
static $func_check = array();
for($index = 0; $index<count($funcs); $index++)
{
    foreach($funcs as $func)
    {
        $times++;
        if(!isset($func_check[$func]))
        {
            if(\function_exists($func)) ;
            $func_check[$func] = 1;
        }
        else $func_check[$func];
    }
}
$s = $b->stop();
$tot+=$s;
echo "<b>Fly Cached : </b><b><span style='color:green'>#$times</span></b> function check took : $s seconds<br />";
$c = new \core\utiles\loadTime;
$times = 0;
$c->start();
/**
 * Function Cached: Has the same logic like Fly Cached section, 
 * But implemented in a function named function_exists_cached()
 **/
for($index = 0; $index<count($funcs); $index++)
{
    foreach($funcs as $func)
    {
        $times++;
        if(\function_exists_cached($func)) ;
    }
}
$s = $c->stop();
$tot+=$s;
echo "<b>Function Cached : </b><b><span style='color:green'>#$times</span></b> function check took : $s seconds<br />";
echo "Total time : $tot seconds";

outputs:

None Cached : #2365444 function check took : 0.69758 seconds
Fly Cached : #2365444 function check took : 0.5307 seconds
Function Cached : #2365444 function check took : 1.02575 seconds
Total time : 2.25403 seconds

Again i wonder to know, considering that function_exists_cached($function_name) has the same implementation of Fly Cached code lines, why does it take that much time??

Upvotes: 0

user149341
user149341

Reputation:

No, it does not. It just checks whether the function is defined in the function table. Simple enough.

However, the Zend Opcache extension may optimize out some calls to function_exists() and certain other functions which can in some cases be evaluated at compile time. (It only optimizes out calls to function_exists() where the function is defined internally by PHP, or by an extension.)

Upvotes: 5

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